HAVING子句允许您指定过滤器的条件,分组结果会出现在最终结果。
WHERE子句所选列的条件,而由GROUP BY子句条件创建分组的HAVING子句。
下面是HAVING子句在查询中的位置:
SELECT
FROM
WHERE
GROUP BY
HAVING
ORDER BY
HAVING子句必须遵循GROUP BY子句中的查询,如果使用也必须先于ORDER BY子句。 下面是SELECT语句,包括HAVING子句的语法:
SELECT column1, column2
FROM table1, table2
WHERE [ conditions ]
GROUP BY column1, column2
HAVING [ conditions ]
ORDER BY column1, column2
考虑CUSTOMERS表具有以下记录:
+----+----------+-----+-----------+----------+
| 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 |
+----+----------+-----+-----------+----------+
下面是示例,这将显示记录age大于或等于2的数据量:
SQL > SELECT ID, NAME, AGE, ADDRESS, SALARY
FROM CUSTOMERS
GROUP BY age
HAVING COUNT(age) >= 2;
这将产生以下结果:
+----+--------+-----+---------+---------+
| ID | NAME | AGE | ADDRESS | SALARY |
+----+--------+-----+---------+---------+
| 2 | Khilan | 25 | Delhi | 1500.00 |
+----+--------+-----+---------+---------+