表Table中的结构是 ID title body url. 要求用一个sql查询将url匹配的排在最前，title匹配的其次，body匹配最后，没有任何字段匹配的，不返回。
思路：在表中每一字段对关键字进行联合查询，通过创建一个临时数值字段进行排序，达到匹配顺序的效果。
Query:
select t.[id],t.mark from
(
select [Table].[id], 3 as mark from [Table] where [Table].[url] like '%2astudio%'
union
select [Table].[id], 2 as mark from [Table] where [Table].[title] like '%2astudio%'
union
select [Table].[id], 1 as mark from [Table] where [Table].[body] like '%2astudio%'
) as t   order by mark desc