MySQL的未知列

Question

为什么我收到此错误：

1054 - 在“字段列表”

未知列“t.type”我有一种被称为在我的表列。我有一个使用别名t的表'测试器'。

SELECT y.*, 
      (SELECT COUNT(*) 
       FROM (SELECT *, 
          CASE t.type 
          WHEN 'Advanced' THEN t.type 
          ELSE 'Non-Advanced' 
          END AS group_type 
         FROM tester) x 
      WHERE x.group_type = y.group_type 
       AND (x.grade1 + x.grade2) >= (y.grade1 + y.grade2)) AS rank 
     FROM (SELECT t.name, 
        t.grade1, 
        t.grade2, 
        t.type, 
        CASE t.type 
        WHEN 'Advanced' THEN t.type 
        ELSE 'Non-Advanced' 
        END AS group_type 
       FROM tester t) y 

OMGPonies，有什么想法吗？

谢谢。

-Laxmidi

Answer 1

/我打了我的额头 - 我的错，对不起。

使用此：

SELECT y.*, 
     (SELECT COUNT(*) 
      FROM (SELECT *, 
         CASE type 
         WHEN 'Advanced' THEN type 
         ELSE 'Non-Advanced' 
         END AS group_type 
        FROM tester) x 
     WHERE x.group_type = y.group_type 
      AND (x.grade1 + x.grade2) >= (y.grade1 + y.grade2)) AS rank 
    FROM (SELECT t.name, 
       t.grade1, 
       t.grade2, 
       t.type, 
       CASE t.type 
       WHEN 'Advanced' THEN t.type 
       ELSE 'Non-Advanced' 
       END AS group_type 
      FROM tester t) y 

Answer 2

子查询错误 - 别名T不是这里定义

  (SELECT *, 
      CASE t.type 
      WHEN 'Advanced' THEN t.type 
      ELSE 'Non-Advanced' 
      END AS group_type 
      FROM tester)x ....