Beispiel #1
0
        public string BuildCommand(ConnectorBase connection)
        {
            if (this.QueryMode == QueryMode.ExecuteStoredProcedure || this.QueryMode == QueryMode.None) return string.Empty;

            StringBuilder sb = new StringBuilder();

            bool ownsConnection = false;
            if (connection == null)
            {
                ownsConnection = true;
                connection = ConnectorBase.NewInstance();
            }
            try
            {
                bool bFirst;

                if (this.QueryMode != QueryMode.None)
                {
                    switch (this.QueryMode)
                    {
                        case QueryMode.Select:
                            {
                                if (Offset > 0 && 
                                    connection.TYPE == ConnectorBase.SqlServiceType.MSSQL &&
                                    !connection.SupportsSelectPaging())
                                {
                                    // Special case for Sql Server where in versions prior to 2012 there was no paging support
                                    BuildSelectForMsSqlPaging(sb, connection);
                                }
                                else if (Offset > 0 && Limit > 0 &&
                                    connection.TYPE == ConnectorBase.SqlServiceType.MSACCESS)
                                {
                                    // Special case for Ms Access where paging is not supported so we do a complex emulation of LIMIT+OFFSET
                                    BuildSelectForMsAccessLimitOffset(sb, connection);
                                }
                                else if (Offset > 0 &&
                                    connection.TYPE == ConnectorBase.SqlServiceType.MSACCESS)
                                {
                                    // Special case for Ms Access where paging is not supported so we do a complex emulation of OFFSET
                                    BuildSelectForMsAccessOffset(sb, connection);
                                }
                                else
                                {
                                    sb.Append(@" SELECT ");

                                    if (IsDistinct) sb.Append(@"DISTINCT ");

                                    if (Limit > 0 && 
                                        (connection.TYPE == ConnectorBase.SqlServiceType.MSACCESS ||
                                        (connection.TYPE == ConnectorBase.SqlServiceType.MSSQL && !(connection.SupportsSelectPaging() && Offset > 0))
                                        ))
                                    {
                                        sb.Append(@"TOP " + Limit);
                                        sb.Append(' ');
                                    }

                                    BuildSelectList(sb, connection);

                                    sb.Append(@" FROM ");
                                    if (Schema != null)
                                    {
                                        if (Schema.DatabaseOwner.Length > 0)
                                        {
                                            sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                            sb.Append('.');
                                        }
                                        sb.Append(connection.WrapFieldName(_SchemaName));
                                    }
                                    else
                                    {
                                        sb.Append(@"(");
                                        if (_FromExpression is dg.Sql.IPhrase)
                                        {
                                            sb.Append(((dg.Sql.IPhrase)_FromExpression).BuildPhrase(connection, this));
                                        }
                                        else sb.Append(_FromExpression);
                                        sb.Append(@") ");
                                        sb.Append(connection.WrapFieldName(_FromExpressionTableAlias));
                                    }

                                    BuildJoin(sb, connection);

                                    if (_ListWhere != null && _ListWhere.Count > 0)
                                    {
                                        sb.Append(@" WHERE ");
                                        _ListWhere.BuildCommand(sb, connection, this, null, null);
                                    }

                                    BuildGroupBy(sb, connection, false);
                                    BuildHaving(sb, connection);
                                    BuildOrderBy(sb, connection, false);

                                    if (connection.TYPE == ConnectorBase.SqlServiceType.MYSQL)
                                    {
                                        if (Limit > 0)
                                        {
                                            sb.Append(@" LIMIT ");
                                            sb.Append(Limit);

                                            // OFFSET is not supported without LIMIT
                                            if (Offset > 0)
                                            {
                                                sb.Append(@" OFFSET ");
                                                sb.Append(Offset);
                                            }
                                        }
                                    }
                                    else if (connection.TYPE == ConnectorBase.SqlServiceType.POSTGRESQL)
                                    {
                                        if (Limit > 0)
                                        {
                                            sb.Append(@" LIMIT ");
                                            sb.Append(Limit);
                                        }
                                        if (Offset > 0)
                                        {
                                            sb.Append(@" OFFSET ");
                                            sb.Append(Offset);
                                        }
                                    }
                                    else if (connection.TYPE == ConnectorBase.SqlServiceType.MSSQL)
                                    {
                                        if (connection.SupportsSelectPaging() && Offset > 0)
                                        {
                                            // If we are in MsSql OFFSET/FETCH mode...

                                            sb.Append(@" OFFSET ");
                                            sb.Append(Offset);
                                            sb.Append(@" ROWS");
                                            if (Limit > 0) 
                                            {
                                                sb.Append(@" FETCH NEXT ");
                                                sb.Append(Limit);
                                                sb.Append(@" ROWS ONLY");
                                            }
                                        }
                                    }

                                    // Done with select query
                                }
                                
                                // Write out supported hints
                                switch (_QueryHint)
                                {
                                    case QueryHint.ForUpdate:
                                        if (connection.TYPE == ConnectorBase.SqlServiceType.MYSQL ||
                                            connection.TYPE == ConnectorBase.SqlServiceType.MSSQL ||
                                            connection.TYPE == ConnectorBase.SqlServiceType.POSTGRESQL)
                                        {
                                            sb.Append(@" FOR UPDATE");
                                        }
                                        break;
                                    case QueryHint.LockInSharedMode:
                                        if (connection.TYPE == ConnectorBase.SqlServiceType.MYSQL)
                                        {
                                            sb.Append(@" LOCK IN SHARED MODE");
                                        }
                                        else if (connection.TYPE == ConnectorBase.SqlServiceType.POSTGRESQL)
                                        {
                                            sb.Append(@" FOR SHARE");
                                        }
                                        break;
                                }
                            }

                            break;
                        case QueryMode.Insert:
                            {
                                sb.Append(@"INSERT INTO ");

                                if (Schema.DatabaseOwner.Length > 0)
                                {
                                    sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                    sb.Append('.');
                                }
                                sb.Append(connection.WrapFieldName(_SchemaName));

                                sb.Append(@" (");
                                bFirst = true;
                                foreach (AssignmentColumn ins in _ListInsertUpdate)
                                {
                                    if (bFirst) bFirst = false;
                                    else sb.Append(',');
                                    sb.Append(connection.WrapFieldName(ins.ColumnName));
                                }
                                if (InsertExpression != null)
                                {
                                    sb.Append(@") ");
                                    sb.Append(InsertExpression);
                                }
                                else
                                {
                                    sb.Append(@") VALUES (");
                                    bFirst = true;
                                    foreach (AssignmentColumn ins in _ListInsertUpdate)
                                    {
                                        if (bFirst) bFirst = false;
                                        else sb.Append(',');
                                        if (ins.SecondType == ValueObjectType.Literal)
                                        {
                                            sb.Append(ins.Second);
                                        }
                                        else if (ins.SecondType == ValueObjectType.Value)
                                        {
                                            if (ins.Second is Query)
                                            {
                                                sb.Append('(');
                                                sb.Append(((Query)ins.Second).BuildCommand(connection));
                                                sb.Append(')');
                                            }
                                            else
                                            {
                                                Query.PrepareColumnValue(Schema.Columns.Find(ins.ColumnName), ins.Second, sb, connection, this);
                                            }
                                        }
                                        else if (ins.SecondType == ValueObjectType.ColumnName)
                                        {
                                            if (ins.SecondTableName != null)
                                            {
                                                sb.Append(connection.WrapFieldName(ins.SecondTableName));
                                                sb.Append(@".");
                                            }
                                            sb.Append(connection.WrapFieldName(ins.Second.ToString()));
                                        }
                                    }
                                    sb.Append(@")");

                                    if (_ListWhere != null && _ListWhere.Count > 0)
                                    {
                                        sb.Append(@" WHERE ");
                                        _ListWhere.BuildCommand(sb, connection, this, null, null);
                                    }
                                }
                            }

                            break;
                        case QueryMode.Update:
                            {
                                bool hasJoins = _ListJoin != null && _ListJoin.Count > 0;

                                sb.Append(@"UPDATE ");

                                if (hasJoins && 
                                    (connection.TYPE == ConnectorBase.SqlServiceType.MSSQL || 
                                    connection.TYPE == ConnectorBase.SqlServiceType.MSACCESS) &&
                                    _FromExpressionTableAlias != null && _FromExpressionTableAlias.Length > 0)
                                {
                                    sb.Append(connection.WrapFieldName(_FromExpressionTableAlias));
                                }
                                else
                                {
                                    if (Schema.DatabaseOwner.Length > 0)
                                    {
                                        sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                        sb.Append('.');
                                    }
                                    sb.Append(connection.WrapFieldName(_SchemaName));

                                    if (_FromExpressionTableAlias != null && _FromExpressionTableAlias.Length > 0)
                                    {
                                        sb.Append(' ');
                                        sb.Append(connection.WrapFieldName(_FromExpressionTableAlias));
                                    }
                                }

                                if (hasJoins)
                                {
                                    if (connection.TYPE == ConnectorBase.SqlServiceType.MYSQL)
                                    {
                                        BuildJoin(sb, connection);
                                    }
                                }

                                bFirst = true;
                                foreach (AssignmentColumn upd in _ListInsertUpdate)
                                {
                                    if (bFirst)
                                    {
                                        sb.Append(@" SET ");
                                        bFirst = false;
                                    }
                                    else sb.Append(',');
                                    sb.Append(connection.WrapFieldName(upd.ColumnName));
                                    sb.Append('=');

                                    if (upd.SecondType == ValueObjectType.Literal)
                                    {
                                        sb.Append(upd.Second);
                                    }
                                    else if (upd.SecondType == ValueObjectType.Value)
                                    {
                                        Query.PrepareColumnValue(Schema.Columns.Find(upd.ColumnName), upd.Second, sb, connection, this);
                                    }
                                    else if (upd.SecondType == ValueObjectType.ColumnName)
                                    {
                                        if (upd.SecondTableName != null)
                                        {
                                            sb.Append(connection.WrapFieldName(upd.SecondTableName));
                                            sb.Append(@".");
                                        }
                                        sb.Append(connection.WrapFieldName(upd.Second.ToString()));
                                    }
                                }

                                if (hasJoins)
                                {
                                    if (connection.TYPE == ConnectorBase.SqlServiceType.MSSQL || 
                                        connection.TYPE == ConnectorBase.SqlServiceType.MSACCESS)
                                    {
                                        sb.Append(@" FROM ");
                                        if (Schema.DatabaseOwner.Length > 0)
                                        {
                                            sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                            sb.Append('.');
                                        }
                                        sb.Append(connection.WrapFieldName(_SchemaName));

                                        if (_FromExpressionTableAlias != null && _FromExpressionTableAlias.Length > 0)
                                        {
                                            sb.Append(' ');
                                            sb.Append(connection.WrapFieldName(_FromExpressionTableAlias));
                                        }

                                        BuildJoin(sb, connection);
                                    }
                                }

                                if (_ListWhere != null && _ListWhere.Count > 0)
                                {
                                    sb.Append(@" WHERE ");
                                    _ListWhere.BuildCommand(sb, connection, this, null, null);
                                }

                                BuildOrderBy(sb, connection, false);
                            }

                            break;
                        case QueryMode.InsertOrUpdate:
                            {
                                if (connection.TYPE == ConnectorBase.SqlServiceType.MYSQL)
                                {
                                    sb.Append(@"REPLACE INTO ");

                                    if (Schema.DatabaseOwner.Length > 0)
                                    {
                                        sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                        sb.Append('.');
                                    }
                                    sb.Append(connection.WrapFieldName(_SchemaName));

                                    sb.Append(@" (");
                                    bFirst = true;
                                    foreach (AssignmentColumn ins in _ListInsertUpdate)
                                    {
                                        if (bFirst) bFirst = false;
                                        else sb.Append(',');
                                        sb.Append(connection.WrapFieldName(ins.ColumnName));
                                    }
                                    if (InsertExpression != null)
                                    {
                                        sb.Append(@") ");
                                        sb.Append(InsertExpression);
                                    }
                                    else
                                    {
                                        sb.Append(@") VALUES (");
                                        bFirst = true;
                                        foreach (AssignmentColumn ins in _ListInsertUpdate)
                                        {
                                            if (bFirst) bFirst = false;
                                            else sb.Append(',');
                                            if (ins.SecondType == ValueObjectType.Literal)
                                            {
                                                sb.Append(ins.Second);
                                            }
                                            else if (ins.SecondType == ValueObjectType.Value)
                                            {
                                                if (ins.Second is Query)
                                                {
                                                    sb.Append('(');
                                                    sb.Append(((Query)ins.Second).BuildCommand(connection));
                                                    sb.Append(')');
                                                }
                                                else
                                                {
                                                    Query.PrepareColumnValue(Schema.Columns.Find(ins.ColumnName), ins.Second, sb, connection, this);
                                                }
                                            }
                                            else if (ins.SecondType == ValueObjectType.ColumnName)
                                            {
                                                if (ins.SecondTableName != null)
                                                {
                                                    sb.Append(connection.WrapFieldName(ins.SecondTableName));
                                                    sb.Append(@".");
                                                }
                                                sb.Append(connection.WrapFieldName(ins.Second.ToString()));
                                            }
                                        }
                                        sb.Append(@")");

                                        if (_ListWhere != null && _ListWhere.Count > 0)
                                        {
                                            sb.Append(@" WHERE ");
                                            _ListWhere.BuildCommand(sb, connection, this, null, null);
                                        }
                                    }
                                }
                                else
                                {
                                    _NeedTransaction = true;

                                    if (connection.TYPE == ConnectorBase.SqlServiceType.POSTGRESQL)
                                    {
                                        throw new NotImplementedException(@"This operation is not implemented for PostgreSQL due to database limitations.");
                                    }

                                    // MSSQL
                                    QueryMode qm = this.QueryMode;
                                    this.QueryMode = QueryMode.Update;

                                    sb.Append(BuildCommand(connection));

                                    sb.Append(@"; IF @@rowcount = 0 BEGIN ");

                                    this.QueryMode = QueryMode.Insert;

                                    sb.Append(BuildCommand(connection));

                                    sb.Append(@"; END");

                                    this.QueryMode = qm;
                                }
                            }
                            break;
                        case QueryMode.Delete:
                            {
                                sb.Append(@"DELETE");
                                if (_ListJoin != null && _ListJoin.Count > 0)
                                {
                                    if (Schema.DatabaseOwner.Length > 0)
                                    {
                                        sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                        sb.Append('.');
                                    }
                                    sb.Append(connection.WrapFieldName(_SchemaName));
                                }
                                sb.Append(@" FROM ");

                                if (Schema.DatabaseOwner.Length > 0)
                                {
                                    sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                    sb.Append('.');
                                }
                                sb.Append(connection.WrapFieldName(_SchemaName));

                                BuildJoin(sb, connection);
                                if (_ListWhere != null && _ListWhere.Count > 0)
                                {
                                    sb.Append(@" WHERE ");
                                    _ListWhere.BuildCommand(sb, connection, this, null, null);
                                }
                                BuildOrderBy(sb, connection, false);
                            }

                            break;
                        case QueryMode.CreateTable:
                            {
                                sb.Append(@"CREATE TABLE ");

                                if (Schema.DatabaseOwner.Length > 0)
                                {
                                    sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                    sb.Append('.');
                                }
                                sb.Append(connection.WrapFieldName(_SchemaName));

                                sb.Append('(');
                                int iPrimaryKeys = 0;
                                bool bSep = false;
                                foreach (TableSchema.Column col in Schema.Columns)
                                {
                                    if (col.IsPrimaryKey) iPrimaryKeys++;
                                    if (bSep) sb.Append(@", "); else bSep = true;
                                    BuildColumnProperties(sb, connection, col, false);
                                }
                                if (iPrimaryKeys > 0)
                                {
                                    if (bSep) sb.Append(@", ");

                                    sb.AppendFormat(@"CONSTRAINT {0} PRIMARY KEY(", connection.WrapFieldName(@"PK_" + _SchemaName));
                                    bSep = false;
                                    foreach (TableSchema.Column col in Schema.Columns)
                                    {
                                        if (!col.IsPrimaryKey) continue;
                                        if (bSep) sb.Append(@", "); else bSep = true;
                                        if (col.IsPrimaryKey) sb.Append(connection.WrapFieldName(col.Name));
                                    }
                                    bSep = true;
                                    sb.Append(')');
                                }

                                sb.Append(')');

                                if (Schema.TableOptions != null && Schema.TableOptions.Count > 0)
                                {
                                    foreach (KeyValuePair<string, string> option in Schema.TableOptions)
                                    {
                                        sb.Append(' ');
                                        sb.Append(option.Key);
                                        sb.Append('=');
                                        sb.Append(option.Value);
                                    }
                                }
                            }
                            break;
                        case QueryMode.CreateIndex:
                            BuildCreateIndex(sb, connection, _CreateIndexObject);
                            break;
                        case QueryMode.CreateIndexes:
                            {
                                if ((Schema.Indexes.Count + Schema.ForeignKeys.Count) > 1)
                                {
                                    _NeedTransaction = true;
                                }
                                foreach (TableSchema.Index index in Schema.Indexes)
                                {
                                    BuildCreateIndex(sb, connection, index);
                                    sb.Append(@";");
                                }
                                foreach (TableSchema.ForeignKey foreignKey in Schema.ForeignKeys)
                                {
                                    BuildCreateIndex(sb, connection, foreignKey);
                                    sb.Append(@";");
                                }
                            }
                            break;
                        case QueryMode.AddColumn:
                            {
                                sb.Append(@"ALTER TABLE ");

                                if (Schema.DatabaseOwner.Length > 0)
                                {
                                    sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                    sb.Append('.');
                                }
                                sb.Append(connection.WrapFieldName(_SchemaName));

                                sb.Append(@" ADD ");

                                if (connection.TYPE == ConnectorBase.SqlServiceType.MYSQL || connection.TYPE == ConnectorBase.SqlServiceType.POSTGRESQL)
                                {
                                    sb.Append(@"COLUMN ");
                                }
                                BuildColumnProperties(sb, connection, _AlterColumn, false);
                                if (connection.TYPE == ConnectorBase.SqlServiceType.MYSQL)
                                {
                                    int idx = Schema.Columns.IndexOf(_AlterColumn);
                                    if (idx == 0) sb.Append(@"FIRST ");
                                    else sb.AppendFormat(@"AFTER {0} ", connection.WrapFieldName(Schema.Columns[idx - 1].Name));
                                }
                            }
                            break;
                        case QueryMode.ChangeColumn:
                            {
                                if (_AlterColumnOldName != null && _AlterColumnOldName.Length == 0) _AlterColumnOldName = null;
                                if (_AlterColumnOldName != null)
                                {
                                    if (connection.TYPE == ConnectorBase.SqlServiceType.MSSQL)
                                    {
                                        sb.Append(@"EXEC sp_rename ");
                                        if (Schema.DatabaseOwner.Length > 0)
                                        {
                                            sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                            sb.Append('.');
                                        }
                                        sb.Append(connection.WrapFieldName(_SchemaName));
                                        sb.Append('.');
                                        sb.Append(connection.WrapFieldName(_AlterColumnOldName));
                                        sb.Append(',');
                                        sb.Append(connection.WrapFieldName(_AlterColumn.Name));
                                        sb.Append(@",'COLUMN';");
                                    }
                                    else if (connection.TYPE == ConnectorBase.SqlServiceType.POSTGRESQL)
                                    {
                                        sb.Append(@"ALTER TABLE ");
                                        if (Schema.DatabaseOwner.Length > 0)
                                        {
                                            sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                            sb.Append('.');
                                        }
                                        sb.Append(connection.WrapFieldName(_SchemaName));
                                        sb.Append(@" RENAME COLUMN ");
                                        sb.Append(connection.WrapFieldName(_AlterColumnOldName));
                                        sb.Append(@" TO ");
                                        sb.Append(connection.WrapFieldName(_AlterColumn.Name));
                                        sb.Append(';');
                                    }
                                }
                                if (connection.TYPE == ConnectorBase.SqlServiceType.POSTGRESQL)
                                {
                                    // Very limited syntax, will have to do this with several statements

                                    sb.Append(@"ALTER TABLE ");
                                    if (Schema.DatabaseOwner.Length > 0)
                                    {
                                        sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                        sb.Append('.');
                                    }
                                    sb.Append(connection.WrapFieldName(_SchemaName));

                                    string alterColumnStatement = @" ALTER COLUMN ";
                                    alterColumnStatement += connection.WrapFieldName(_AlterColumn.Name);

                                    sb.Append(alterColumnStatement);
                                    sb.Append(@" TYPE ");
                                    bool isTextField; // UNUSED HERE
                                    BuildColumnPropertiesDataType(sb, connection, _AlterColumn, out isTextField);
                                    sb.Append(',');

                                    sb.Append(alterColumnStatement);
                                    sb.Append(_AlterColumn.Nullable ? @" DROP NOT NULL;" : @" SET NOT NULL;");

                                    sb.Append(alterColumnStatement);
                                    sb.Append(@" SET DEFAULT ");
                                    Query.PrepareColumnValue(_AlterColumn, _AlterColumn.Default, sb, connection, this);
                                    sb.Append(';');
                                }
                                else
                                {
                                    sb.Append(@"ALTER TABLE ");
                                    if (Schema.DatabaseOwner.Length > 0)
                                    {
                                        sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                        sb.Append('.');
                                    }
                                    sb.Append(connection.WrapFieldName(_SchemaName));
                                    sb.Append(' ');
                                    if (connection.TYPE == ConnectorBase.SqlServiceType.MYSQL)
                                    {
                                        sb.AppendFormat(@"CHANGE {0} ", connection.WrapFieldName(_AlterColumnOldName != null ? _AlterColumnOldName : _AlterColumn.Name));
                                    }
                                    else
                                    {
                                        sb.Append(@"ALTER COLUMN ");
                                    }
                                    BuildColumnProperties(sb, connection, _AlterColumn, connection.TYPE == ConnectorBase.SqlServiceType.MSSQL);
                                    if (connection.TYPE == ConnectorBase.SqlServiceType.MYSQL)
                                    {
                                        int idx = Schema.Columns.IndexOf(_AlterColumn);
                                        if (idx == 0) sb.Append(@"FIRST ");
                                        else sb.AppendFormat(@"AFTER {0} ", connection.WrapFieldName(Schema.Columns[idx - 1].Name));
                                    }
                                }
                            }
                            break;
                        case QueryMode.DropColumn:
                            {
                                sb.Append(@"ALTER TABLE ");
                                if (Schema.DatabaseOwner.Length > 0)
                                {
                                    sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                    sb.Append('.');
                                }
                                sb.Append(connection.WrapFieldName(_SchemaName));
                                sb.Append(@" DROP COLUMN ");
                                sb.Append(connection.WrapFieldName(_DropColumnName));
                            }
                            break;
                        case QueryMode.DropForeignKey:
                            {
                                if (connection.TYPE == ConnectorBase.SqlServiceType.MYSQL)
                                {
                                    sb.Append(@"ALTER TABLE ");
                                    if (Schema.DatabaseOwner.Length > 0)
                                    {
                                        sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                        sb.Append('.');
                                    }
                                    sb.Append(connection.WrapFieldName(_SchemaName));
                                    sb.Append(@" DROP FOREIGN KEY ");
                                    sb.Append(connection.WrapFieldName(_DropColumnName));
                                }
                                else if (connection.TYPE == ConnectorBase.SqlServiceType.POSTGRESQL)
                                {
                                    sb.Append(@"ALTER TABLE ");
                                    if (Schema.DatabaseOwner.Length > 0)
                                    {
                                        sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                        sb.Append('.');
                                    }
                                    sb.Append(connection.WrapFieldName(_SchemaName));
                                    sb.Append(@" DROP CONSTRAINT ");
                                    sb.Append(connection.WrapFieldName(_DropColumnName));
                                }
                                else
                                {
                                    sb.Append(@"ALTER TABLE ");
                                    if (Schema.DatabaseOwner.Length > 0)
                                    {
                                        sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                        sb.Append('.');
                                    }
                                    sb.Append(connection.WrapFieldName(_SchemaName));
                                    sb.Append(@" DROP CONSTRAINT ");
                                    sb.Append(connection.WrapFieldName(_DropColumnName));
                                }
                            }
                            break;
                        case QueryMode.DropIndex:
                            {
                                if (connection.TYPE == ConnectorBase.SqlServiceType.MYSQL || connection.TYPE == ConnectorBase.SqlServiceType.POSTGRESQL)
                                {
                                    sb.Append(@"ALTER TABLE ");
                                    if (Schema.DatabaseOwner.Length > 0)
                                    {
                                        sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                        sb.Append('.');
                                    }
                                    sb.Append(connection.WrapFieldName(_SchemaName));
                                    sb.Append(@" DROP INDEX ");
                                    sb.Append(connection.WrapFieldName(_DropColumnName));
                                }
                                else
                                {
                                    sb.Append(@"ALTER TABLE ");
                                    if (Schema.DatabaseOwner.Length > 0)
                                    {
                                        sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                        sb.Append('.');
                                    }
                                    sb.Append(connection.WrapFieldName(_SchemaName));
                                    sb.Append(@" DROP CONSTRAINT ");
                                    sb.Append(connection.WrapFieldName(_DropColumnName));
                                }
                            }
                            break;
                        case QueryMode.DropTable:
                            {
                                sb.Append(@"DROP TABLE ");
                                if (Schema.DatabaseOwner.Length > 0)
                                {
                                    sb.Append(connection.WrapFieldName(Schema.DatabaseOwner));
                                    sb.Append('.');
                                }
                                sb.Append(connection.WrapFieldName(_SchemaName));
                            }
                            break;
                    }
                }
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                if (ownsConnection && connection != null)
                {
                    connection.Close();
                    connection.Dispose();
                    connection = null;
                }
            }

            return sb.ToString();
        }