Question

我需要确定客户是否使用SQL查询购买了100种或更多独特的饮料，到目前为止我已经做过：

     SELECT COUNT(DISTINCT beer_id)
     FROM Orders
     WHERE patron_email='smith@gmail.com'

我如何测试这个结果是100还是更多？

更新：对于模糊的问题，我很抱歉，我需要使用标准的SQL。

Answer 1

使用having子句，如：

SELECT COUNT(DISTINCT beer_id)
FROM Orders
WHERE patron_email='smith@gmail.com'
having count(distinct beer_id) > 100

Answer 2

您可以将CASE与产生单行的子查询一起使用：

SELECT CASE WHEN (SELECT COUNT(DISTINCT beer_id)
                 FROM Orders
                 WHERE patron_email='smith@gmail.com') > 100 
                 THEN 'More than 100' ELSE 'Not more than 100' END As ColumnName

Answer 3

这适用于MySQL，不确定其他人：

 SELECT COUNT(DISTINCT beer_id) > 100
 FROM Orders
 WHERE patron_email='smith@gmail.com'

在SELECT中添加一个布尔条件。它将评估为0表示false或1表示true。

Answer 4

试试这个：

SELECT COUNT(beer_id)
     FROM Orders
     WHERE patron_email='smith@gmail.com'
group by beer_id
having COUNT(beer_id) > 100

Answer 5

或另外一个：

select case when (count(distinct beer_id)>100) then 1
        else 0 end
    from orders where patron_email='.....'

Answer 6

假设T-SQL

DECLARE @result AS INT
DECLARE @boolean AS INT

SET @result = ( SELECT COUNT(DISTINCT beer_id)
                FROM Orders
                WHERE patron_email='smith@gmail.com')

IF @result > 100
    BEGIN
        SET @boolean = 1
    END
ELSE
    BEGIN
        SET @boolean = 0
    END

Answer 7

EXISTS运算符产生一个布尔值：

SELECT EXISTS (
    SELECT 12345
    FROM orders
    GROUP BY customer_id
    HAVING COUNT(beer_id) > 100
    ) AS at_least_one_customer_ordered_100_different_beers
    ;

从SQL查询中获取true / false

7 个答案: