Question

我需要帮助验证mysql中的空值或空值我试图在我的情况下使用这种方式，但不起作用：

SELECT
    CASE 
          WHEN account_type      IS NULL THEN 'Uninformed'
          WHEN account_type = ''         THEN 'Empty '
    END as Type,
COUNT(accounts.id)                     AS Total
FROM
accounts

有谁知道如何解决这个问题？

Answer 1

SELECT
CASE WHEN account_type IS NULL THEN 'Uninformed'
     WHEN account_type = ''  THEN 'Empty '
END as Type,
COUNT(accounts.id) AS Total
FROM accounts
group by account_type

您缺少group by条款。

Answer 2

您的查询是正确的。最后，您需要添加group by account_type;。

查询应该是这样的。

SELECT 
CASE WHEN account_type IS NULL THEN 'Uninformed'
        WHEN account_type = '' THEN 'Empty '
END AS Type,
COUNT(accounts.id) AS Total
FROM    accounts
GROUP BY account_type

Answer 3

在没有case语句的情况下编写相同查询的另一种流畅方式就是......

SELECT ISNULL(NULLIF(ISNULL(account_type , 'Uninformed'),''),'Empty') AS Type
     ,COUNT(accounts.id)                     AS Total
FROM accounts
GROUP BY ISNULL(NULLIF(ISNULL(account_type , 'Uninformed'),''),'Empty')

MySQL检查空白或空值

3 个答案: