我在选择查询中有一个选择查询，该查询引发错误：“用作表达式的子查询返回的不止一行”[重复]

Question

我正在尝试显示多个内容，例如用户 ID、薪水等。 我使用了一个 select 语句来做到这一点。在这个 select 语句中，我需要使用另一个 select 语句来提供“工资的分数”。分数的查询是正确的。当我尝试将此选择用于主选择时，它会给出错误“超过一行返回...” 样本数据：

//sample data
insert into employee(id_user int,salary_date date,salary_value) values 
(3, 2017-06-28, 15)
( 5, 2017-06-26 5)
( 2, 2017-06-20 5)
( 1, 2017-06-20 15)
( 4, 2017-06-17 25)

//expected output:
id date       sal  newdate   days aboveavgsal     date     current/firstsal 
1  2017-06-20 15  2017-05-20   31   N           2017-04-20    0.6
1  2017-05-20 10  2017-04-20   30   N           2017-04-20    0.4
1  2017-04-20 20  2017-03-20   31   Y           2017-03-20    0.8
1  2017-03-20 20  2017-02-20   28   Y           NULL          0.8
1  2017-02-20 15  NULL         NULL N           NULL          0.6

    SELECT  id_user
            , salary_date
            , salary_value
            , lead(salary_date) OVER(PARTITION BY id_user ORDER BY salary_date desc)
            , salary_date::timestamp - lead(salary_date::timestamp) over (PARTITION BY id_user ORDER BY salary_date DESC)
            , CASE WHEN salary_value >= 20 THEN 'Y' ELSE 'N' END
            , CASE WHEN salary_value >= 20 THEN lead(salary_date) OVER(PARTITION BY id_user ORDER BY salary_date DESC) END
            , (SELECT CAST(t1.salary_value AS float) / CAST(t.salary_value AS float) 
               FROM (
                     SELECT  t.id_user
                             , t.salary_value
                             , ROW_NUMBER() OVER(PARTITION BY t.id_user ORDER BY t.salary_date) AS rowrank
                     FROM employee t
                    ) AS t
                    INNER JOIN employee AS t1 ON t1.id_user = t.id_user
                    WHERE t.rowrank = 1
                    GROUP BY t1.id_user, t1.salary_value, t1.salary_date, t.salary_value, t.rowrank
                    ORDER BY t1.id_user, t1.salary_date DESC
              ) AS fraction
    FROM employee


Error starts in this query which i tried enclosing in braces.

    (SELECT  CAST(t1.salary_value AS float) / CAST(t.salary_value AS float) 
     FROM (
           SELECT t.id_user
                  , t.salary_value
                  , row_number() OVER(PARTITION BY t.id_user ORDER BY t.salary_date ) AS rowrank
           FROM employee t) AS t
           INNER JOIN employee t1 ON t1.id_user = t.id_user
           WHERE t.rowrank = 1
           GROUP BY t1.id_user, t1.salary_value, t1.salary_date, t.salary_value, t.rowrank
           ORDER BY t1.id_user, t1.salary_date DESC
          )

Answer 1

在你声明的这一部分

(SELECT  CAST(t1.salary_value AS float) / CAST(t.salary_value AS float)

演员要求 t1.salary 是一个单一的值。

但是这部分返回的不止一行。

       SELECT t.id_user
              , t.salary_value
              , row_number() OVER(PARTITION BY t.id_user ORDER BY t.salary_date ) AS rowrank
       FROM employee t) AS t
       INNER JOIN employee t1 ON t1.id_user = t.id_user
       WHERE t.rowrank = 1
       GROUP BY t1.id_user, t1.salary_value, t1.salary_date, t.salary_value, t.rowrank
       ORDER BY t1.id_user, t1.salary_date DESC