Question

我在mysql数据库中有3个表名为Visits，Groups，Carers。访问可以由小组或护理人员执行，因此在访问表中我有一个字段护理者模式，如果访问由访问者执行则设置为1，如果由组执行则设置为0。

我需要构建一个语句来检索组名或者看护者名称（取决于carer_mode的值）

我意识到下面的代码不正确，但它可能有助于解释我想要实现的逻辑：

SELECT CASE carer_mode
WHEN  '1' THEN (SELECT name FROM carers WHERE Carers.id = Visits.carer_id )
WHEN '0' THEN (SELECT name FROM groups WHERE Groups.id = Visits.carer_id )
END as carer_name
FROM `Visits`

我很感激任何帮助我实现目标的有效代码的帮助

感谢

凯文

Answer 1

您的代码似乎很好。这是获得相同结果的另一种方法：

    SELECT g.name
    FROM 
        Visits AS v
      JOIN
        Groups AS g
          ON g.id = v.carer_id
    WHERE v.carer_mode = 0
UNION ALL
    SELECT c.name
    FROM 
        Visits AS v
      JOIN
        Carers AS c
          ON c.id = v.carer_id
    WHERE v.carer_mode = 1

Answer 2

我认为这会奏效：

  select 
  case carer_mode when '1' then c.name 
  else g.name end as carer_name 
  from Carer c 
  left join Visits v on v.carer_id=c.carer_id 
  left join Groups g on g.carer_id=c.carer_id

mysql条件查询

2 个答案: