Question

我有一个带有marital_status字段的用户表，其值为0-5：
（0-单
1，结婚
2-离异
3，丧偶
4-关系）

我正在尝试对此表运行一个select查询，并输出marital_status字段的相应值而不是数字。

这是我正在使用的查询：

   SELECT user_id,user_first_name, user_last_name,user_email_1,IF(user_gender="0","Male","Female")     AS user_gender,
user_birthdate,
CASE WHEN user_marital_status=0 THEN "Single" END AS user_marital_status, CASE WHEN    user_marital_status = 1 THEN "Married" END AS user_marital_status,
CASE WHEN user_marital_status=2 THEN "Divorced" END AS user_marital_status, CASE WHEN   user_marital_status = 3 THEN "Widowed" END AS user_marital_status,
CASE WHEN user_marital_status = 4 THEN "In a relationship" END  AS user_marital_status
FROM users a

但是，当我运行此查询时，它为user_marital_status创建了5个不同的列如何让marital_status只是一个具有不同值的列？

Answer 1

您需要一个包含多个case子句的when子句：

SELECT user_id,
       user_first_name, 
       user_last_name,
       user_email_1,
       IF(user_gender="0","Male","Female") AS user_gender,
       user_birthdate,
       CASE user_marital_status 
           WHEN 0 THEN 'Single'
           WHEN 1 THEN 'Married'
           WHEN 2 THEN 'Divorced'
           WHEN 3 THEN 'Widowed'
           WHEN 4 THEN 'In a relationship'
       END AS user_marital_status
FROM   users a

MySQL案例选择查询

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