加入两个表

Question

我有两张桌子：

user:

id   username       name
1aa   sample.user    Sample User   

和credential:

id  userId  type         value
1   1aa     salt         abc123
2   1aa     password     samplehashpassword

我想执行查询以获得以下结果（每个用户一行）：

userId  username      name            type      value     type        value
1aa     sample.user   Sample User     salt      abc123    password    samplehashpassword   

现在我正在执行这个查询：

SELECT
    "userId", username, name, type, value
FROM
    public.user u 
INNER JOIN public.credential c
    ON u.id = c."userId";
    

这会导致：

userId  username      name            type      value
1aa     sample.user   Sample User     salt      abc123

userId  username      name            type      value
1aa     sample.user   Sample User     password  samplehashpassword  

我想要一个用户的单行。我怎样才能做到这一点？

Answer 1

你可以使用两个joins：

SELECT u.*, cs.type, cs.value, cp.type, cp.value
FROM public.user u INNER JOIN
     public.credential cs
     ON u.id = cs."userId" AND cs.type = 'salt' INNER JOIN
     public.credential cp
     ON u.id = cp."userId" AND cp.type = 'password';