一、 表 SC 如下:
1. 执行如下 SQL 文:
select SNO from SC group by SNO
结果为:
1
2
3
+++++++++++++++++++++++++++++++++++++++++++++++
++++++++++++++++
2. 执行如下 SQL 文:
select SNO ,count(SNO) from SC group by SNO
结果为:
SNO count(SNO)
1 4
2 3
3 2
+++++++++++++++++++++++++++++++++++++++++++++++
++++++++++++++++
3. 执行如下 SQL 文:
select SNO from SC group by SNO having count(SNO)=2
结果为:
3
+++++++++++++++++++++++++++++++++++++++++++++++