如果没有找到行，则返回默认值 [英] Return Default value if no row found

问题描述

我正在构建查询以从数据库中搜索多行，例如

I'm building query to search multiple rows from database like

SELECT 
  * 
FROM
  table1 
WHERE col1 = '012311' 
  OR col1 = '0123631' 
  OR col1 = '091233' 
  OR col1 = '092111' 

这里它返回前 3 个值，因为它们存在于表中，但最后一个不返回任何值，因为它不在表中.那么如果没有找到该值的行，我该如何在查询中设置我的默认值?

Here it returns first 3 values because they are present in the table but it returns nothing for last one because it's not in table. So how can I set my default value in the query if no row is found for that value?

推荐答案

有几种方法，取决于数据集.这是一种方法:

There are several approaches, which depend on the dataset. Here's one way:

SELECT *, 
IFNULL(
    ( SELECT col1 FROM table1 
        WHERE col1 IN ('012311','0123631','091233','092111') 
    ),
    'some_value'
) AS my_col1
FROM table1;

不一定要复制+粘贴，您必须根据具体情况进行调整.

Not neccessarily copy+paste, you will have to adjust for your specific case.

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