sql语法收集
先看两张表softball table
id name
1 a
2 b
3 c
4 d
football table
--------
id name
1 a
2 c
3 k
4 g
union 和union all 区别
select name from softball
union
select name from football
rs:
name
=--------
a
b
c
d
k
g
union 区别出两张表重复的数据
select name from softball
union all
select name from football
name
-------
a
b
c
d
a
c
k
g
union all 区别所有的数据。
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