SQL HAVING 子句 SQL 注入 SQL 事务 SQL HAVING 子句 HAVING 子句使你能够指定过滤条件,从而控制查询结果中哪些组可以出现在最终结果里面。 WHERE 子句对被选择的列施加条件,而 HAVING 子句则对 GROUP BY 子句所产生的组施加条件。 语法: 下面可以看到 HAVING 子句在 SELECT 查询中的位置: SELECT FROM WHERE GROUP BY HAVING ORDER BY 在 SELECT 查询中,HAVING 子句必须紧随 GROUP BY 子句,并出现在 ORDER BY 子句(如果有的话)之前。带有 HAVING 子句的 SELECT 语句的语法如下所示: SELECT column1, column2 FROM table1, table2 WHERE [ conditions ] GROUP BY column1, column2 HAVING [ conditions ] ORDER BY column1, column2 示例: 考虑 CUSTOMERS 表,表中的记录如下所示: +----+----------+-----+-----------+----------+ | ID | NAME | AGE | ADDRESS | SALARY | +----+----------+-----+-----------+----------+ | 1 | Ramesh | 32 | Ahmedabad | 2000.00 | | 2 | Khilan | 25 | Delhi | 1500.00 | | 3 | kaushik | 23 | Kota | 2000.00 | | 4 | Chaitali | 25 | Mumbai | 6500.00 | | 5 | Hardik | 27 | Bhopal | 8500.00 | | 6 | Komal | 22 | MP | 4500.00 | | 7 | Muffy | 24 | Indore | 10000.00 | +----+----------+-----+-----------+----------+ 下面是一个有关 HAVING 子句使用的实例,该实例将会筛选出出现次数大于或等于 2 的所有记录。 SQL > SELECT ID, NAME, AGE, ADDRESS, SALARY FROM CUSTOMERS GROUP BY age HAVING COUNT(age) >= 2; 其执行结果如下所示: +----+--------+-----+---------+---------+ | ID | NAME | AGE | ADDRESS | SALARY | +----+--------+-----+---------+---------+ | 2 | Khilan | 25 | Delhi | 1500.00 | +----+--------+-----+---------+---------+ SQL 注入 SQL 事务