SQLite HAVING 子句
SQLite HAVING 子句
HAVING 子句对 GROUP BY 子句设置条件的方式与 WHERE 和 SELECT 的交互方式类似。HAVING 搜索条件在进行分组操作之后应用。 HAVING 可以包含聚合函数。HAVING 子句可以引用选择列表中显示的任意项。
语法
SELECT FROM WHERE GROUP BY HAVING ORDER BY
HAVING子句必须跟随查询中的GROUP BY子句,如果使用,还必须在ORDER BY子句之前。以下是SELECT语句的语法,包括HAVING子句。
SELECT column1, column2 FROM table1, table2 WHERE [ conditions ] GROUP BY column1, column2 HAVING [ conditions ] ORDER BY column1, column2
例子
假设COMPANY表包含如下数据:
ID NAME AGE ADDRESS SALARY ---------- ---------- ---------- ---------- ---------- 1 Paul 32 California 20000.0 2 Allen 25 Texas 15000.0 3 Teddy 23 Norway 20000.0 4 Mark 25 Rich-Mond 65000.0 5 David 27 Texas 85000.0 6 Kim 22 South-Hall 45000.0 7 James 24 Houston 10000.0 8 Paul 24 Houston 20000.0 9 James 44 Norway 5000.0 10 James 45 Texas 5000.0
下面是将显示name计数小于2的记录的示例。
sqlite > SELECT * FROM COMPANY GROUP BY name HAVING count(name) < 2;
这将产生以下结果。
ID NAME AGE ADDRESS SALARY ---------- ---------- ---------- ---------- ---------- 2 Allen 25 Texas 15000 5 David 27 Texas 85000 6 Kim 22 South-Hall 45000 4 Mark 25 Rich-Mond 65000 3 Teddy 23 Norway 20000
下面是将显示name计数大于2的记录的示例。
sqlite > SELECT * FROM COMPANY GROUP BY name HAVING count(name) > 2;
这将产生以下结果。
ID NAME AGE ADDRESS SALARY ---------- ---------- ---------- ---------- ---------- 10 James 45 Texas 5000