sqlite having 子句

having 子句允許指定條件來過濾將出現(xiàn)在最終結(jié)果中的分組結(jié)果。

where 子句在所選列上設(shè)置條件，而 having 子句則在由 group by 子句創(chuàng)建的分組上設(shè)置條件。

1. 語法

下面是 having 子句在 select 查詢中的位置：

select
from
where
group by
having
order by

在一個查詢中，having 子句必須放在 group by 子句之后，必須放在 order by 子句之前。下面是包含 having 子句的 select 語句的語法：

select column1, column2
from table1, table2
where [ conditions ]
group by column1, column2
having [ conditions ]
order by column1, column2

2. 范例

假設(shè) company 表有以下記錄：

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

下面是一個范例，它將顯示名稱計(jì)數(shù)小于 2 的所有記錄：

sqlite > select * from company group by name having count(name) < 2;

這將產(chǎn)生以下結(jié)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

下面是一個范例，它將顯示名稱計(jì)數(shù)大于 2 的所有記錄：

sqlite > select * from company group by name having count(name) > 2;

這將產(chǎn)生以下結(jié)果：

id          name        age         address     salary
----------  ----------  ----------  ----------  ----------
10          james       45          texas       5000