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-- 使用 greatest 函数求最大值
SQL>
SQL> create table test(a int, b int, c int);
Table created
SQL> begin
2 insert into test values(11,12,13) ;
3 insert into test values(21,22,16) ;
4 insert into test values(33,12,10) ;
5 end ;
6 /
PL/SQL procedure successfully completed
SQL> select greatest(a, b, c) max_value from test ;
MAX_VALUE
----------
13
22
33
SQL> drop table test purge ;
Table dropped
SQL>
mysql> select @@version ;
+------------+
| @@version |
+------------+
| 5.6.21-log |
+------------+
1 row in set (0.00 sec)
mysql>
mysql> create table test(a int, b int, c int);
Query OK, 0 rows affected (0.01 sec)
mysql>
mysql> insert into test values(11,12,13) ;
Query OK, 1 row affected (0.00 sec)
mysql> insert into test values(21,22,16) ;
Query OK, 1 row affected (0.00 sec)
mysql> insert into test values(33,12,10) ;
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> select greatest(a, b, c) max_value from test ;
+-----------+
| max_value |
+-----------+
| 13 |
| 22 |
| 33 |
+-----------+
3 rows in set (0.00 sec)
mysql>
mysql> drop table test ;
Query OK, 0 rows affected (0.01 sec)
mysql>