[code="sql"]
select column1,column2 from table1 left join table on .... where 条件
union
select column1,column2 from table2 left join table on .... where 条件
union
select column1,column2 from table3 left join table on .... where 条件
[/code]
只有 table1,table2,table3 不一样,其他都一样,这类的SQL 有优化的余地么?