确定我是否应该合并的案例声明 [英] Case statement to determine if I should union

问题描述

我目前想做某种条件联合.给出以下示例:

I currently want to do some sort of conditional union. Given the following example:

SELECT  age, name
FROM    users
UNION
SELECT  25 AS age, 'Betty' AS name

说我想只在'users'的数量> = 2时才合并第二个语句，否则不要将两者合并.

Say I wanted to only union the second statement if the count of 'users' was >=2 , otherwise do not union the two.

总而言之，如果表仅具有2个或更多值，我想在表后附加一行.

In summary I want to append a table with a row if the table only has 2 or more values.

推荐答案

您可以使用类似这样的丑陋的hack ，但我认为

You could use an ugly hack something like this, but I think Tim's answer is better:

SELECT  age, name
FROM    users
UNION ALL

SELECT 25 AS age, 'Betty' AS name
WHERE (SELECT COUNT(*) FROM users) > 1

这篇关于确定我是否应该合并的案例声明的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！