Question

我正在迁移数据库，我需要将整数列更改为字符串格式的相关类别。如何使用ifelse或switch / case / break来检查每个值并动态更改？

SELECT *, Category FROM Members
  Category =
  Switch(category)
  if (value == 1 then change to "Category 1", value == 2 then change to "Category 2 and so on.)

Answer 1

SELECT *, case when category = 1 then 'Category 1'
               when category = 2 then 'Category 2'
               else 'Category unknown'
          end as category
FROM Members

Answer 2

MySQL的CASE子句可以做到这一点。

UPDATE `Members`
    Set `Category` = CASE `Value`
        WHEN '1' THEN 'Category 1'
        WHEN '2' THEN 'Category 2'
    END
WHERE `Value` IN ('1','2');

这意味着任何带有Value = '1'的和所有行现在也会有Category = 'Category 1'。您可以根据需要使此查询更具体。

使用大小写更改值

2 个答案: