表PERSON
id name
1 A
2 A
3 B
4 C
5 B
作用一个列:
select distinct name from PERSON
结果:
A
B
C
作用多个列:必须相同的记录才排除
select distinct id,name from PERSON
结果:
1 A
2 A
3 B
4 C
5 B
表PERSON
id name
1 A
2 A
3 B
4 C
5 B
作用一个列:
select distinct name from PERSON
结果:
A
B
C
作用多个列:必须相同的记录才排除
select distinct id,name from PERSON
结果:
1 A
2 A
3 B
4 C
5 B