JOIN 或任何其他附近的 PostgreSQL 语法错误

Question

我在 PostgreSQL 数据库中导入了这个奥林匹克数据集。我想使用 select 语句创建 table 并且还有更多内容。但我收到此错误：

ERROR: column foo.age does not exist LINE 17: (case when foo.Age=NULL then foo.Age=26 else foo.Age end... ^ HINT: Perhaps you meant to reference the column "ae.age". SQL state: 42703 Character: 628

我打算做的是：

更改年龄、身高、体重列的类型
获取上述数据并将其与我要替换 NULL 值的另一个查询结合起来
使用以上两个数据创建新的 table。所有这些都一次性完成。我对这个数据库还是个新手，我实际上是在 SQLite 中完成的，它工作得很好，但在这里它不会工作。如果您有任何其他方法可以做到这一点，请告诉我。谢谢你！这是我的代码：

CREATE TABLE Female_participants AS 
SELECT DISTINCT
   ae.id AS Player_id,
   ae.Name,
   ( /* Here what i want to do is im thinking like foo table which i joined to this table is giving me 
       (this and following column where i want to replace NULL values) age,weight and height as int,float,float */
      CASE
         WHEN/*foo.age suppose to be column from foo table which is casted to int*/
            foo.Age = NULL 
         THEN
            foo.Age = 26 
         ELSE
            foo.Age 
      END
   )
   AS Age , 
   (
      CASE
         WHEN/*foo.height suppose to be float*/
            foo.height = NULL 
         THEN
            FLOOR(AVG(foo.height)) 
         ELSE
            foo.height 
      END
   )
   AS Height, 
   (
      CASE
         WHEN /*foo.Weight suppose to be float*/
            foo.weight = NULL 
         THEN
            FLOOR(AVG(foo.weight)) 
         ELSE
            foo.weight 
      END
   )
   AS weight, City, Team AS Country 
FROM
   athlete_events ae 
   INNER JOIN
      (
         SELECT DISTINCT
            id,
            /*Here i want to convert the dtype from TEXT to int or float*/
            CAST(age AS INT) thag,
            CAST(height AS FLOAT) AS thht,
            CAST(weight AS FLOAT) AS thwt 
         FROM
            athlete_events /* i read on https://www.postgresqltutorial.com/.. that i can self-join table */
      )
      AS foo /*Joining this table on id*/
      ON foo.id = ae.id 
GROUP BY
   id,
   name

Answer 1

你的代码有两个问题：

关系“foo”实际上没有“年龄”列，它的列是 id,thag,thht,thwt
运算符“smth = NULL”不存在，必须使用 smth IS NULL 或对此处的简单情况使用 COALESCE 函数代码可以是这样的：

    CREATE TABLE Female_participants AS 
    SELECT DISTINCT
       ae.id AS Player_id, 
       ae.Name, 
       COALESCE(foo.Age, 26) AS Age , 
       COALESCE(foo.height, foo_avg.height) AS Height, 
       COALESCE(foo.weight, foo_avg.weight) AS weight, 
       City, 
       Team AS Country 
    FROM athlete_events AS ae 
    INNER JOIN (
        SELECT DISTINCT
           id,
           age::INT,
           height::FLOAT,
           weight::FLOAT 
        FROM athlete_events
    ) AS foo ON foo.id = ae.id 
    INNER JOIN (
        SELECT
           AVG(height::FLOAT) AS height,
           AVG(weight::FLOAT) AS weight
        FROM athlete_events
    ) AS foo_avg ON TRUE;

Answer 2

问题取决于以下事实：当子查询 athlete_avents 时，您将 age、height 和 weight 列重命名为 thag、thht、thwt。

所以在您的 CASE 块中，您应该使用重命名的列名，而不是原来的列名。

I.E.

   ( /* Here what i want to do is im thinking like foo table which i joined to this table is giving me 
       (this and following column where i want to replace NULL values) age,weight and height as int,float,float */
      CASE
         WHEN/*foo.age suppose to be column from foo table which is casted to int*/
            foo.thag= NULL 
         THEN
            foo.thag = 26 
         ELSE
            foo.thag
      END
   )
   AS Age , 
   (
      CASE
         WHEN/*foo.height suppose to be float*/
            foo.thht= NULL 
         THEN
            FLOOR(AVG(foo.thht)) 
         ELSE
            foo.thht
      END
   )
   AS Height, 
   (
      CASE
         WHEN /*foo.Weight suppose to be float*/
            foo.thwt = NULL 
         THEN
            FLOOR(AVG(foo.thwt )) 
         ELSE
            foo.thwt 
      END
   )
   AS weight

Answer 3

您的查询或多或少可以归结为：

SELECT DISTINCT
   ae.id AS Player_id,
   ae.Name,
   coalesce( foo.age::int ,26 ) ::int  AS Age , 
   coalesce( foo.height::float , FLOOR(AVG(foo.height::float ) over())::float ) ::float  AS Height , 
   coalesce( foo.weight::float , FLOOR(AVG(foo.weight::float ) over())::float ) ::float  AS Weight , 
   City,
   Team AS Country 
FROM
   athlete_events foo ;

尝试阅读以下 coalesce , double colon cast , and aggregate function without group by clause 的链接。

JOIN 或任何其他附近的 PostgreSQL 语法错误

PostgreSQL Syntax Error near JOIN, or anyother

sql

postgresql

join

column-alias