如果没有找到行，则返回默认值

本文介绍了如果没有找到行，则返回默认值的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 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.