两个表中都有UserName字段,现在需要两个表中所有的UserName,如何做?select distinct UserName from table1
union all
select distinct UserName from table2
这个不能剔除两个合并以后重复的,要怎么解决?
union all
select distinct UserName from table2
这个不能剔除两个合并以后重复的,要怎么解决?
union
select distinct UserName from table2
union
select UserName from table2
--返回两个表的所有的UserName ,且去掉重复的
union
select UserName from table2
union all
select distinct UserName from table2
--返回量表的所有的UserName ,即使两表重复的也不去掉distinct 只用去去掉当前查询的表的重复行
select UserName from tbl1
union
select UserName from tbl2
--union all 是不去重的
select distinct UserName from table1
union
select distinct UserName from table2