标签：style blog io color sp div on log cti
1.AVG()
用法：求平均值
举例：
mysql> select * from t1; +----+------+----------+---------+-------+-------+ | id | name | password | test001 | test3 | test4 | +----+------+----------+---------+-------+-------+ | 2 | 1 | 1 | 1 | 1 | 1 | | 3 | 3 | 4 | 5 | 6 | 7 | | 4 | 3 | 4 | 5 | 6 | 7 | | 5 | 3 | 4 | 5 | 6 | 7 | | 6 | 3 | 4 | 5 | 6 | 7 | | 7 | 3 | 4 | 5 | 6 | 7 | | 8 | 3 | 4 | 5 | 6 | 7 | | 9 | 3 | 4 | 5 | 6 | 7 | | 10 | 3 | 4 | 5 | 6 | 7 | +----+------+----------+---------+-------+-------+ 9 rows in set (0.00 sec) mysql> select AVG(id) from t1; +---------+ | AVG(id) | +---------+ | 6.0000 | +---------+ 1 row in set (0.00 sec)
2.COUNT()
用法：记录的条数
举例：
mysql> select COUNT(id) from t1; +-----------+ | COUNT(id) | +-----------+ | 9 | +-----------+ 1 row in set (0.00 sec)
3.MAX()
用法：返回最大值
举例：
mysql> select MAX(id) from t1; +---------+ | MAX(id) | +---------+ | 10 | +---------+ 1 row in set (0.01 sec)
4.MIN()
用法：返回最小值
举例：
mysql> select MIN(id) from t1; +---------+ | MIN(id) | +---------+ | 2 | +---------+ 1 row in set (0.00 sec)
5.SUM()
用法：求和
举例：
mysql> select SUM(id) from t1; +---------+ | SUM(id) | +---------+ | 54 | +---------+ 1 row in set (0.00 sec)
其他：MD5(),PASSWORD()
mysql> select MD5(‘MYSQL‘); +----------------------------------+ | MD5(‘MYSQL‘) | +----------------------------------+ | 14498b83dd1667a0c78f4fdaf5afbf4b | +----------------------------------+ 1 row in set (0.00 sec) mysql> select PASSWORD(‘MYSQL‘); +-------------------------------------------+ | PASSWORD(‘MYSQL‘) | +-------------------------------------------+ | *A97AF8E14502C1B988202FB7B96CF565B6523F9D | +-------------------------------------------+ 1 row in set (0.00 sec) mysql> select ENCYPT(‘MYSQL‘); ERROR 1305 (42000): FUNCTION test.ENCYPT does not exist mysql> select ENCRYPT(‘MYSQL‘); +------------------+ | ENCRYPT(‘MYSQL‘) | +------------------+ | NULL | +------------------+ 1 row in set (0.03 sec)
标签：style blog io color sp div on log cti
原文地址：http://www.cnblogs.com/zhangminghui/p/4077423.html
