/// <summary>
/// 解析 SELECT 命令
/// </summary>
/// <param name="dbQuery">查询语义</param>
/// <param name="indent">缩进</param>
/// <param name="isOuter">指示是最外层查询</param>
/// <param name="token">解析上下文</param>
/// <returns></returns>
protected override RawCommand ResolveSelectCommand(IDbQueryableInfo_Select dbQuery, int indent, bool isOuter, ResolveToken token)
{
var cmd = (MappingCommand)this.ResolveSelectCommandImpl(dbQuery, indent, isOuter, token);
cmd.CombineFragments();
if (isOuter)
{
cmd.JoinFragment.Append(';');
}
return(cmd);
}
/// <summary>
/// 初始化 <see cref="ColumnExpressionVisitor"/> 类的新实例
/// </summary>
public ColumnExpressionVisitor(IDbQueryProvider provider, TableAliasCache aliases, IDbQueryableInfo_Select qQuery)
: base(provider, aliases, qQuery.Select.Expressions != null ? qQuery.Select.Expressions[0] : null)
{
_provider = provider;
_aliases = aliases;
_qQuery = qQuery;
_groupBy = qQuery.GroupBy;
_include = qQuery.Includes;
if (_pickColumns == null)
{
_pickColumns = new ColumnCollection();
}
_navigations = new NavigationCollection();
_navChainHopper = new List <string>(10);
}
/// <summary>
/// 初始化 <see cref="ColumnExpressionVisitor"/> 类的新实例
/// </summary>
/// <param name="provider">查询语义提供者</param>
/// <param name="aliases">表别名集合</param>
/// <param name="dbQuery">查询语义</param>
public ColumnExpressionVisitor(IDbQueryProvider provider, TableAlias aliases, IDbQueryableInfo_Select dbQuery)
: base(provider, aliases, dbQuery.Select.Expressions != null ? dbQuery.Select.Expressions[0] : null)
{
_provider = provider;
_aliases = aliases;
_dbQuery = dbQuery;
_groupBy = dbQuery.GroupBy;
_include = dbQuery.Includes;
if (_pickColumns == null)
{
_pickColumns = new DbColumnCollection();
}
_navDescriptors = new NavDescriptorCollection();
_navDescriptorKeys = new List <string>(10);
}
/// <summary>
/// 生成关联子句所表示的别名列表
/// </summary>
/// <param name="dbQuery">查询语义</param>
/// <param name="token">解析上下文</param>
/// <returns></returns>
protected TableAlias PrepareTableAlias(IDbQueryableInfo_Select dbQuery, ResolveToken token)
{
var aliases = new TableAlias((dbQuery.Joins != null ? dbQuery.Joins.Count : 0) + 1, token != null ? token.AliasPrefix : null);
foreach (DbExpression exp in dbQuery.Joins)
{
// [INNER/LEFT JOIN]
if (exp.DbExpressionType == DbExpressionType.GroupJoin || exp.DbExpressionType == DbExpressionType.Join || exp.DbExpressionType == DbExpressionType.GroupRightJoin)
{
this.PrepareJoinAlias(exp, aliases);
}
else if (exp.DbExpressionType == DbExpressionType.SelectMany)
{
this.PrepareCrossAlias(exp, aliases);
}
}
return(aliases);
}
/// <summary>
/// 初始化 <see cref="OracleDbQueryableInfo_Select"/> 类的新实例
/// </summary>
public OracleDbQueryableInfo_Select(IDbQueryableInfo_Select source)
: base()
{
this.Joins = source.Joins;
this.OrderBys = source.OrderBys;
this.Includes = source.Includes;
this.HasDistinct = source.HasDistinct;
this.HasAny = source.HasAny;
this.HasMany = source.HasMany;
this.Skip = source.Skip;
this.Take = source.Take;
this.FromType = source.FromType;
this.Select = source.Select;
this.Where = source.Where;
this.Having = source.Having;
this.Aggregate = source.Aggregate;
this.GroupBy = source.GroupBy;
this.Subquery = source.Subquery;
this.IsParsedByMany = source.IsParsedByMany;
this.Unions = source.Unions;
}
// 构造由一对多关系产生的嵌套查询
static IDbQueryableInfo_Select ParseOutQuery(IDbQueryableInfo_Select dbQuery)
{
// @havePaging 是否有分页信息
if (dbQuery == null || dbQuery.Select == null)
{
return(dbQuery);
}
Expression select = dbQuery.Select.Expressions[0];
List <DbExpression> includes = dbQuery.Includes;
Type fromType = dbQuery.FromType;
// 解析导航属性 如果有 1:n 的导航属性，那么查询的结果集的主记录将会有重复记录
// 这时就需要使用嵌套语义，先查主记录，再关联导航记录
Expression myExpression = select;
var lambdaExpression = myExpression as LambdaExpression;
if (lambdaExpression != null)
{
myExpression = lambdaExpression.Body;
}
var initExpression = myExpression as MemberInitExpression;
var newExpression = myExpression as NewExpression;
bool hasMany = DbQueryParser.IsHasMany(includes);
if (!hasMany)
{
hasMany = initExpression != null && IsHasMany(initExpression);
}
#region 嵌套语义
if (hasMany)
{
newExpression = initExpression != null ? initExpression.NewExpression : newExpression;
List <MemberBinding> bindings = new List <MemberBinding>();
if (initExpression != null)
{
bindings = initExpression.Bindings.ToList(x => x, x => TypeUtils.IsPrimitiveType((x.Member as System.Reflection.PropertyInfo).PropertyType));
}
if (newExpression != null || bindings.Count() > 0)
{
// 简化内层选择器，只选择最小字段，不选择导航字段，导航字段在外层加进去
initExpression = Expression.MemberInit(newExpression, bindings);
lambdaExpression = Expression.Lambda(initExpression, lambdaExpression.Parameters);
dbQuery.Select = new DbExpression(DbExpressionType.Select, lambdaExpression);
}
dbQuery.IsParsedByMany = true;
dbQuery.Includes = new List <DbExpression>(0);
var result_Query = new DbQueryableInfo_Select();
result_Query.FromType = fromType;
result_Query.Subquery = dbQuery;
result_Query.Joins = new List <DbExpression>(0);
result_Query.OrderBys = new List <DbExpression>(0);
result_Query.Includes = includes;
result_Query.HasMany = true;
result_Query.Select = new DbExpression(DbExpressionType.Select, select);
#region 排序
if (dbQuery.OrderBys.Count > 0)
{
// 是否有分页
bool havePaging = (dbQuery.Take > 0 || dbQuery.Skip > 0);
if (!havePaging)
{
// 如果没有分页，则OrderBy需要放在外层
result_Query.OrderBys = dbQuery.OrderBys;
dbQuery.OrderBys = new List <DbExpression>(0);
}
else
{
// 如果有分页，只有主表/用到的1:1从表放在内层，其它放在外层
List <DbExpression> innerOrderBy = null;
foreach (var dbExpression in dbQuery.OrderBys)
{
hasMany = IsHasMany(dbExpression.Expressions[0] as LambdaExpression);
if (!hasMany)
{
if (innerOrderBy == null)
{
innerOrderBy = new List <DbExpression>();
}
innerOrderBy.Add(dbExpression);
}
}
if (innerOrderBy != null && innerOrderBy.Count > 0)
{
result_Query.OrderBys = dbQuery.OrderBys;
dbQuery.OrderBys = innerOrderBy;
}
}
}
#endregion
#region 分组
if (dbQuery.GroupBy != null)
{
// 查看外层是否需要重新构造选择器。如果有分组并且有聚合函数，则需要重新构造选择器。否则外层解析不了聚合函数
// demo => line 1280
bool newSelector = bindings.Any(x => ((MemberAssignment)x).Expression.NodeType == ExpressionType.Call) || newExpression.Arguments.Any(x => x.NodeType == ExpressionType.Call);
if (newSelector)
{
ParameterExpression newParameter = null;
List <DbExpression> dbExpressions = null;
if (result_Query.Includes != null && result_Query.Includes.Count > 0)
{
dbExpressions = result_Query.Includes;
}
else if (result_Query.OrderBys != null && result_Query.OrderBys.Count > 0)
{
dbExpressions = result_Query.OrderBys;
}
if (dbExpressions != null && dbExpressions.Count > 0)
{
newParameter = (dbExpressions[0].Expressions[0] as LambdaExpression).Parameters[0];
}
// 1对多导航嵌套查询外层的的第一个表别名固定t0，参数名可随意
var parameterExpression = newParameter != null ? newParameter : Expression.Parameter(newExpression.Type, "__g");
bindings = bindings.ToList(x => (MemberBinding)Expression.Bind(x.Member, Expression.MakeMemberAccess(parameterExpression, x.Member)));
List <Expression> arguments = null;
if (newExpression.Members != null)
{
arguments = new List <Expression>(newExpression.Arguments.Count);
for (int i = 0; i < newExpression.Arguments.Count; i++)
{
var member = newExpression.Members[i];
var arg = Expression.MakeMemberAccess(parameterExpression, member);
arguments.Add(arg);
}
}
newExpression = Expression.New(newExpression.Constructor, arguments, newExpression.Members);
initExpression = Expression.MemberInit(newExpression, bindings);
lambdaExpression = Expression.Lambda(initExpression, parameterExpression);
result_Query.Select = new DbExpression(DbExpressionType.Select, lambdaExpression);
}
}
#endregion
dbQuery = result_Query;
}
#endregion
return(dbQuery);
}
// 创建 SELECT 命令
RawCommand ResolveSelectCommandImpl(IDbQueryableInfo_Select dbQuery, int indent, bool isOuter, ResolveToken token)
{
// 说明：
// 1.OFFSET 前必须要有 'ORDER BY'，即 'Skip' 子句前必须使用 'OrderBy' 子句
// 2.在有聚合函数的<MAX,MIN...>情况下，如果有 'Distinct' 'GroupBy' 'Skip' 'Take' 子句，则需要使用嵌套查询
// 3.'Any' 子句将翻译成 IF EXISTS...
// 4.分组再分页时需要使用嵌套查询，此时子查询不需要 'OrderBy' 子句，但最外层则需要
// 5.'Skip' 'Take' 子句视为语义结束符，在其之后的子句将使用嵌套查询
// 6.导航属性中有 1:n 关系的，需要使用嵌套查询，否则分页查询会有问题
// 导航属性中有1:n关系，只统计主表
// 例：AccountList = a.Client.AccountList,
var subQuery = dbQuery.Subquery as IDbQueryableInfo_Select;
if (dbQuery.HasMany && subQuery != null && subQuery.Aggregate != null)
{
dbQuery = subQuery;
}
bool useStatis = dbQuery.Aggregate != null;
bool useNesting = dbQuery.HasDistinct || dbQuery.GroupBy != null || dbQuery.Skip > 0 || dbQuery.Take > 0;
string alias0 = token != null && !string.IsNullOrEmpty(token.AliasPrefix) ? (token.AliasPrefix + "0") : "t0";
// 没有聚合函数或者使用 'Skip' 子句，则解析OrderBy
// 导航属性如果使用嵌套，除非有 TOP 或者 OFFSET 子句，否则不能用ORDER BY
bool useOrderBy = (!useStatis || dbQuery.Skip > 0) && !dbQuery.HasAny && (!dbQuery.IsParsedByMany || (dbQuery.Skip > 0 || dbQuery.Take > 0));
TableAlias aliases = this.PrepareTableAlias(dbQuery, token);
var result = new MappingCommand(this, aliases, token)
{
HasMany = dbQuery.HasMany
};
ISqlBuilder jf = result.JoinFragment;
ISqlBuilder wf = result.WhereFragment;
jf.Indent = indent;
#region 嵌套查询
if (useStatis && useNesting)
{
// SELECT
jf.Append("SELECT ");
jf.AppendNewLine();
// SELECT COUNT(1)
var visitor_ = new AggregateExpressionVisitor(this, aliases, dbQuery.Aggregate, dbQuery.GroupBy, alias0);
visitor_.Write(jf);
result.AddNavMembers(visitor_.NavMembers);
// SELECT COUNT(1) FROM
jf.AppendNewLine();
jf.Append("FROM ( ");
indent += 1;
jf.Indent = indent;
}
#endregion
#region 择子句
// SELECT 子句
if (jf.Indent > 0)
{
jf.AppendNewLine();
}
jf.Append("SELECT ");
if (dbQuery.HasAny)
{
jf.Append("CASE WHEN COUNT(1) = 1 THEN 1 ELSE 0 END FROM (");
indent += 1;
jf.Indent = indent;
jf.AppendNewLine();
jf.Append("SELECT 1 ");
}
if (useStatis && !useNesting)
{
// 如果有聚合函数，并且不是嵌套的话，则直接使用SELECT <MAX,MIN...>，不需要解析选择的字段
jf.AppendNewLine();
var visitor_ = new AggregateExpressionVisitor(this, aliases, dbQuery.Aggregate, dbQuery.GroupBy);
visitor_.Write(jf);
result.AddNavMembers(visitor_.NavMembers);
}
else
{
// DISTINCT 子句
if (dbQuery.HasDistinct)
{
jf.Append("DISTINCT ");
}
#region 择字段
if (!dbQuery.HasAny)
{
// SELECT 范围
var visitor2 = new SQLiteColumnExpressionVisitor(this, aliases, dbQuery);
visitor2.Write(jf);
result.PickColumns = visitor2.PickColumns;
result.PickColumnText = visitor2.PickColumnText;
result.PickNavDescriptors = visitor2.PickNavDescriptors;
result.AddNavMembers(visitor2.NavMembers);
}
#endregion
}
#endregion
#region 顺序解析
// FROM 子句
jf.AppendNewLine();
jf.Append("FROM ");
if (dbQuery.Subquery != null)
{
// 子查询
jf.Append('(');
RawCommand cmd = this.ResolveSelectCommandImpl(dbQuery.Subquery, indent + 1, false, token);
jf.Append(cmd.CommandText);
jf.AppendNewLine();
jf.Append(") ");
jf.Append(alias0);
jf.Append(' ');
}
else
{
var typeRuntime = TypeRuntimeInfoCache.GetRuntimeInfo(dbQuery.FromType);
jf.AppendMember(typeRuntime.TableName, !typeRuntime.IsTemporary);
jf.Append(' ');
jf.Append(alias0);
jf.Append(' ');
}
// LEFT<INNER> JOIN 子句
ExpressionVisitorBase visitor = new JoinExpressionVisitor(this, aliases, dbQuery.Joins);
visitor.Write(jf);
wf.Indent = jf.Indent;
// WHERE 子句
visitor = new WhereExpressionVisitor(this, aliases, dbQuery.Where);
visitor.Write(wf);
result.AddNavMembers(visitor.NavMembers);
// GROUP BY 子句
visitor = new GroupByExpressionVisitor(this, aliases, dbQuery.GroupBy);
visitor.Write(wf);
result.AddNavMembers(visitor.NavMembers);
// HAVING 子句
visitor = new HavingExpressionVisitor(this, aliases, dbQuery.Having, dbQuery.GroupBy);
visitor.Write(wf);
result.AddNavMembers(visitor.NavMembers);
// ORDER 子句
if (dbQuery.OrderBys.Count > 0 && useOrderBy)
{
visitor = new OrderByExpressionVisitor(this, aliases, dbQuery.OrderBys, dbQuery.GroupBy);
visitor.Write(wf);
result.AddNavMembers(visitor.NavMembers);
}
#endregion
#region 分页查询
if (dbQuery.Take > 0)
{
wf.AppendNewLine().AppendFormat("LIMIT {0}", this.DbValue.GetSqlValue(dbQuery.Take, token));
}
else if (dbQuery.Take == 0 && dbQuery.Skip > 0)
{
wf.AppendNewLine().AppendFormat("LIMIT {0}", this.DbValue.GetSqlValue(-1, token));
}
if (dbQuery.Skip > 0)
{
wf.AppendFormat(" OFFSET {0}", this.DbValue.GetSqlValue(dbQuery.Skip, token));
}
#endregion
#region 嵌套查询
if (useStatis && useNesting)
{
result.CombineFragments();
indent -= 1;
jf.Indent = indent;
jf.AppendNewLine();
jf.Append(") ");
jf.Append(alias0);
}
#endregion
#region 嵌套导航
// TODO Include 从表，没分页，OrderBy 报错
if (dbQuery.HasMany && subQuery != null && subQuery.OrderBys.Count > 0 && subQuery.Aggregate == null && !(subQuery.Skip > 0 || subQuery.Take > 0))
{
result.CombineFragments();
visitor = new OrderByExpressionVisitor(this, aliases, subQuery.OrderBys);//, null, "t0");
visitor.Write(jf);
}
#endregion
#region 并集查询
// UNION 子句
if (dbQuery.Unions != null && dbQuery.Unions.Count > 0)
{
result.CombineFragments();
for (int index = 0; index < dbQuery.Unions.Count; index++)
{
jf.AppendNewLine();
jf.Append("UNION ALL");
if (indent == 0)
{
jf.AppendNewLine();
}
RawCommand cmd = this.ResolveSelectCommand(dbQuery.Unions[index], indent, isOuter, token);
jf.Append(cmd.CommandText);
}
}
#endregion
#region Any 子句
// 'Any' 子句
if (dbQuery.HasAny)
{
// 产生 WHERE 子句
result.CombineFragments();
// 如果没有分页，则显式指定只查一笔记录
if (dbQuery.Take == 0 && dbQuery.Skip == 0)
{
jf.AppendNewLine();
jf.Append("LIMIT 1");
}
indent -= 1;
jf.Indent = indent;
jf.AppendNewLine();
jf.Append(") ");
jf.Append(alias0);
}
#endregion
return(result);
}
RawCommand ResolveSelectCommandImpl(IDbQueryableInfo_Select dbQuery, int indent, bool isOuter, ResolveToken token)
{
// 说明：
// 1.OFFSET 前必须要有 'ORDER BY'，即 'Skip' 子句前必须使用 'OrderBy' 子句
// 2.在有聚合函数的<MAX,MIN...>情况下，如果有 'Distinct' 'GroupBy' 'Skip' 'Take' 子句，则需要使用嵌套查询
// 3.'Any' 子句将翻译成 IF EXISTS...
// 4.分组再分页时需要使用嵌套查询，此时子查询不需要 'OrderBy' 子句，但最外层则需要
// 5.'Skip' 'Take' 子句视为语义结束符，在其之后的子句将使用嵌套查询
// 6.导航属性中有 1:n 关系的，需要使用嵌套查询，否则分页查询会有问题
// 8.如果只有 Skip 没有 Take，则使用 Row_Number() Over()分页语法，其它使用 LIMIT ## OFFSET 语法
// 导航属性中有1:n关系，只统计主表
// 例：AccountList = a.Client.AccountList,
var subQuery = dbQuery.Subquery as IDbQueryableInfo_Select;
if (dbQuery.HasMany && subQuery != null && subQuery.Aggregate != null)
{
dbQuery = subQuery;
}
bool useStatis = dbQuery.Aggregate != null;
// 没有聚合函数或者使用 'Skip' 子句，则解析OrderBy
// 导航属性如果使用嵌套，除非有 TOP 或者 OFFSET 子句，否则不能用ORDER BY
string alias0 = token != null && !string.IsNullOrEmpty(token.AliasPrefix) ? (token.AliasPrefix + "0") : "t0";
bool useSubquery = dbQuery.HasDistinct || dbQuery.GroupBy != null || dbQuery.Skip > 0 || dbQuery.Take > 0;
bool useOrderBy = (!useStatis || dbQuery.Skip > 0) && !dbQuery.HasAny && (!dbQuery.IsParsedByMany || (dbQuery.Skip > 0 || dbQuery.Take > 0));
TableAlias aliases = this.PrepareTableAlias(dbQuery, token);
var result = new MappingCommand(this, aliases, token)
{
HasMany = dbQuery.HasMany
};
ISqlBuilder jf = result.JoinFragment;
ISqlBuilder wf = result.WhereFragment;
ISqlBuilder sf = null;
jf.Indent = indent;
#region 嵌套查询
if (useStatis && useSubquery)
{
// SELECT
jf.Append("SELECT ");
jf.AppendNewLine();
// SELECT COUNT(1)
var visitor_ = new AggregateExpressionVisitor(this, aliases, dbQuery.Aggregate, dbQuery.GroupBy, alias0);
visitor_.Write(jf);
result.AddNavMembers(visitor_.NavMembers);
// SELECT COUNT(1) FROM
jf.AppendNewLine();
jf.Append("FROM ( ");
indent += 1;
jf.Indent = indent;
}
#endregion
#region 择子句
// SELECT 子句
if (jf.Indent > 0)
{
jf.AppendNewLine();
}
jf.Append("SELECT ");
if (dbQuery.HasAny)
{
jf.Append("CASE WHEN COUNT(1) = 1 THEN 1 ELSE 0 END FROM (");
indent += 1;
jf.Indent = indent;
jf.AppendNewLine();
jf.Append("SELECT 1 ");
}
if (useStatis && !useSubquery)
{
// 如果有聚合函数，并且不是嵌套的话，则直接使用SELECT <MAX,MIN...>，不需要解析选择的字段
jf.AppendNewLine();
var visitor_ = new AggregateExpressionVisitor(this, aliases, dbQuery.Aggregate, dbQuery.GroupBy);
visitor_.Write(jf);
result.AddNavMembers(visitor_.NavMembers);
}
else
{
// DISTINCT 子句
if (dbQuery.HasDistinct)
{
jf.Append("DISTINCT ");
}
#region 择字段
if (!dbQuery.HasAny)
{
// SELECT 范围
var visitor_ = new ColumnExpressionVisitor(this, aliases, dbQuery);
if (dbQuery.Skip > 0 && dbQuery.Take == 0)
{
sf = this.CreateSqlBuilder(token);
sf.Indent = jf.Indent + 1;
visitor_.Write(sf);
}
else
{
visitor_.Write(jf);
}
result.PickColumns = visitor_.PickColumns;
result.PickColumnText = visitor_.PickColumnText;
result.PickNavDescriptors = visitor_.PickNavDescriptors;
result.AddNavMembers(visitor_.NavMembers);
if (sf != null)
{
// 第一层嵌套
int index = 0;
jf.AppendNewLine();
foreach (var column in result.PickColumns)
{
jf.AppendMember(alias0, column.Name);
jf.AppendAs(column.NewName);
index += 1;
if (index < result.PickColumns.Count)
{
jf.Append(',');
jf.AppendNewLine();
}
}
jf.AppendNewLine();
jf.Append("FROM(");
// 第二层嵌套
indent += 1;
jf.Indent = indent;
jf.AppendNewLine();
jf.Append("SELECT");
jf.Append(sf);
jf.Append(',');
jf.AppendNewLine();
if (dbQuery.OrderBys.Count == 0)
{
throw new XFrameworkException("The method 'OrderBy' must be called before 'Skip'.");
}
jf.Append("ROW_NUMBER() OVER(");
var visitor3 = new OrderByExpressionVisitor(this, aliases, dbQuery.OrderBys, dbQuery.GroupBy);
visitor3.Write(jf, false);
result.AddNavMembers(visitor3.NavMembers);
jf.Append(") Row_Number0");
}
}
#endregion
}
#endregion
#region 顺序解析
// FROM 子句
jf.AppendNewLine();
jf.Append("FROM ");
if (dbQuery.Subquery != null)
{
// 子查询
jf.Append("(");
var cmd = this.ResolveSelectCommandImpl(dbQuery.Subquery, indent + 1, false, token);
jf.Append(cmd.CommandText);
jf.AppendNewLine();
jf.Append(") ");
jf.Append(alias0);
jf.Append(' ');
}
else
{
var typeRuntime = TypeRuntimeInfoCache.GetRuntimeInfo(dbQuery.FromType);
jf.AppendMember(typeRuntime.TableName, !typeRuntime.IsTemporary);
jf.Append(' ');
jf.Append(alias0);
jf.Append(' ');
}
// LEFT<INNER> JOIN 子句
ExpressionVisitorBase visitor = new JoinExpressionVisitor(this, aliases, dbQuery.Joins);
visitor.Write(jf);
wf.Indent = jf.Indent;
// WHERE 子句
visitor = new WhereExpressionVisitor(this, aliases, dbQuery.Where);
visitor.Write(wf);
result.AddNavMembers(visitor.NavMembers);
// GROUP BY 子句
visitor = new GroupByExpressionVisitor(this, aliases, dbQuery.GroupBy);
visitor.Write(wf);
result.AddNavMembers(visitor.NavMembers);
// HAVING 子句
visitor = new HavingExpressionVisitor(this, aliases, dbQuery.Having, dbQuery.GroupBy);
visitor.Write(wf);
result.AddNavMembers(visitor.NavMembers);
// ORDER 子句
if (dbQuery.OrderBys.Count > 0 && useOrderBy)// && !groupByPaging)
{
visitor = new OrderByExpressionVisitor(this, aliases, dbQuery.OrderBys, dbQuery.GroupBy);
visitor.Write(wf);
result.AddNavMembers(visitor.NavMembers);
}
#endregion
#region 分页查询
// LIMIT 子句可以被用于强制 SELECT 语句返回指定的记录数。
// LIMIT 接受一个或两个数字参数。参数必须是一个整数常量。如果给定两个参数，第一个参数指定第一个返回记录行的偏移量，第二个参数指定返回记录行的最大数目。
// 初始记录行的偏移量是 0(而不是 1)： 为了与 PostgreSQL 兼容，MySQL 也支持句法： LIMIT # OFFSET #。
// Limit n,-1 语法不支持，使用ROW_Number()语法代替
if (dbQuery.Take > 0)
{
wf.AppendNewLine().AppendFormat("LIMIT {0}", this.DbValue.GetSqlValue(dbQuery.Take, token));
wf.AppendFormat(" OFFSET {0}", this.DbValue.GetSqlValue(dbQuery.Skip, token));
}
#endregion
#region 嵌套查询
if (useStatis && useSubquery)
{
result.CombineFragments();
indent -= 1;
jf.Indent = indent;
jf.AppendNewLine();
jf.Append(") ");
jf.Append(alias0);
}
#endregion
#region 嵌套导航
// TODO Include 从表，没分页，OrderBy 报错
if (dbQuery.HasMany && subQuery != null && subQuery.OrderBys.Count > 0 && subQuery.Aggregate == null && !(subQuery.Skip > 0 || subQuery.Take > 0))
{
result.CombineFragments();
visitor = new OrderByExpressionVisitor(this, aliases, subQuery.OrderBys);//, null, "t0");
visitor.Write(jf);
}
#endregion
#region 并集查询
// UNION 子句
if (dbQuery.Unions != null && dbQuery.Unions.Count > 0)
{
result.CombineFragments();
for (int index = 0; index < dbQuery.Unions.Count; index++)
{
jf.AppendNewLine();
jf.Append("UNION ALL");
if (indent == 0)
{
jf.AppendNewLine();
}
RawCommand cmd = this.ResolveSelectCommandImpl(dbQuery.Unions[index], indent, isOuter, token);
jf.Append(cmd.CommandText);
}
}
#endregion
#region 分页查询
if (sf != null)
{
// 合并 WHERE
result.CombineFragments();
indent -= 1;
jf.Indent = indent;
jf.AppendNewLine();
jf.Append(") ");
jf.Append(alias0);
jf.AppendNewLine();
jf.Append("WHERE ");
if (dbQuery.Skip > 0)
{
jf.AppendMember(alias0, "Row_Number0");
jf.Append(" > ");
jf.Append(this.DbValue.GetSqlValue(dbQuery.Skip, token));
}
}
#endregion
#region Any 子句
// 'Any' 子句
if (dbQuery.HasAny)
{
// 产生 WHERE 子句
result.CombineFragments();
// 如果没有分页，则显式指定只查一笔记录
if (dbQuery.Take == 0 && dbQuery.Skip == 0)
{
jf.AppendNewLine();
jf.Append("LIMIT 0,1");
}
indent -= 1;
jf.Indent = indent;
jf.AppendNewLine();
jf.Append(") ");
jf.Append(alias0);
}
#endregion
return(result);
}
/// <summary>
/// 初始化 <see cref="OracleColumnExpressionVisitor"/> 类的新实例
/// </summary>
/// <param name="provider">查询语义提供者</param>
/// <param name="aliases">表别名集合</param>
/// <param name="dbQuery">查询语义</param>
public OracleColumnExpressionVisitor(IDbQueryProvider provider, TableAlias aliases, IDbQueryableInfo_Select dbQuery)
: base(provider, aliases, dbQuery)
{
_dbQuery = dbQuery;
}
/// <summary> /// 解析 SELECT 命令 /// </summary> /// <param name="dbQuery">查询语义</param> /// <param name="indent">缩进</param> /// <param name="isOuter">指示是最外层查询</param> /// <param name="token">解析上下文</param> /// <returns></returns> protected abstract RawCommand ResolveSelectCommand(IDbQueryableInfo_Select dbQuery, int indent, bool isOuter, ResolveToken token);
