mysql 数据操作 单表查询 having 过滤 练习
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1. 查询各岗位内包含的员工个数小于2的岗位名、岗位内包含员工名字、个数
mysql> select post,group_concat(name),count(id) from employee group by post; +-----------+-------------------------------------------------+-----------+ | post | group_concat(name) | count(id) | +-----------+-------------------------------------------------+-----------+ | operation | 程咬铁,程咬铜,程咬银,程咬金,张野 | 5 | | sale | 格格,星星,丁丁,丫丫,歪歪 | 5 | | teacher | 成龙,jinxin,jingliyang,liwenzhou,yuanhao,alex | 6 | +-----------+-------------------------------------------------+-----------+ 3 rows in set (0.00 sec) mysql> select post,group_concat(name),count(id) from employee group by post having count(id) <2 ; Empty set (0.05 sec)
3. 查询各岗位平均薪资大于10000的岗位名、平均工资
mysql> select post,avg(salary) from employee group by post having avg(salary) > 10000; +-----------+---------------+ | post | avg(salary) | +-----------+---------------+ | operation | 16800.026000 | | teacher | 175766.718333 | +-----------+---------------+ 2 rows in set (0.04 sec)
4. 查询各岗位平均薪资大于10000且小于20000的岗位名、平均工资
mysql> select post,avg(salary) from employee group by post having avg(salary) between 10000 and 20000; +-----------+--------------+ | post | avg(salary) | +-----------+--------------+ | operation | 16800.026000 | +-----------+--------------+ 1 row in set (0.00 sec)
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