/// <summary>
/// 解释 ORDER BY 子句。
/// </summary>
/// <param name="DbParameters">用于缓存在解释过程中可能会产生的参数。</param>
/// <returns></returns>
public override string Parsing(ref List <IDbDataParameter> DbParameters)
{
OrderByBlock orderBy = (OrderByBlock)this.Description;
StringBuilder cBuffer = new StringBuilder(" ORDER BY");
orderBy.Field.DescriptionParserAdapter = orderBy.DescriptionParserAdapter;
cBuffer.AppendFormat(" {0}", orderBy.Field.GetParser().Parsing(ref DbParameters));
switch (orderBy.Sort)
{
case OrderByMode.ASC:
cBuffer.AppendFormat(" ASC");
break;
default:
cBuffer.AppendFormat(" DESC");
break;
}
return(cBuffer.ToString());
}
/// <summary>
/// 分布关键的命令部份解释。
/// </summary>
/// <param name="sBlock">SELECT命令段描述对象。</param>
/// <param name="DbParameters">用于缓存在解释过程中可能会产生的参数。</param>
/// <returns></returns>
private string ParsingCore(SelectBlock sBlock, ref List <IDbDataParameter> DbParameters)
{
bool AppendComma = true; // 用于标识每个段后是否添加逗号。
sBlock.Blocks[0].DescriptionParserAdapter = sBlock.DescriptionParserAdapter;
string item_buf = sBlock.Blocks[0].GetParser().Parsing(ref DbParameters);
if (item_buf[0] == (char)0x20)
{
item_buf = item_buf.Remove(0, 1);
}
StringBuilder FieldsBuffer = new StringBuilder(item_buf); // 查询的字段信息部份
StringBuilder OtherBuffer = new StringBuilder(); // 除字段信息之外的其它子句部份
OrderByBlock OverOrderBy = null;
for (int i = 1; i < sBlock.Blocks.Count; ++i)
{
if (sBlock.Blocks[i] is FromBlock || sBlock.Blocks[i] is WhereBlock || sBlock.Blocks[i] is GroupByBlock)
{
AppendComma = false;
}
if (sBlock.Blocks[i] is OrderByBlock)
{
AppendComma = false;
OverOrderBy = (OrderByBlock)sBlock.Blocks[i];
continue; // 不在内嵌SELECT子句中生成 ORDER BY 子句（否则会产生查询错误）
}
sBlock.Blocks[i].DescriptionParserAdapter = sBlock.DescriptionParserAdapter;
item_buf = sBlock.Blocks[i].GetParser().Parsing(ref DbParameters);
if (AppendComma)
{
if (item_buf[0] == (char)0x20)
{
FieldsBuffer.AppendFormat(",{0}", item_buf);
}
else
{
FieldsBuffer.AppendFormat(", {0}", item_buf);
}
}
else
{
if (item_buf[0] == (char)0x20)
{
OtherBuffer.Append(item_buf);
}
else
{
OtherBuffer.AppendFormat(" {0}", item_buf);
}
}
}
if (OverOrderBy == null)
{
if (IsNull(sBlock.Pager.HelpField))
{
throw (new Exception("解释分页时失败：没有提供排序字段。"));
}
OverOrderBy = new OrderByBlock();
OverOrderBy.Field = sBlock.Pager.HelpField;
OverOrderBy.Sort = sBlock.Pager.HelpSort;
}
StringBuilder SqlCore = new StringBuilder("WITH [PAGE_TEMP] AS (SELECT ");
OverOrderBy.DescriptionParserAdapter = sBlock.DescriptionParserAdapter;
SqlCore.AppendFormat("{0}, ROW_NUMBER() OVER({1}) AS [ROWNUM]", FieldsBuffer, OverOrderBy.GetParser().Parsing(ref DbParameters));
SqlCore.Append(OtherBuffer);
SqlCore.AppendFormat(") ");
return(SqlCore.ToString());
}