SQLITE "no such column"(如果由 "AS"创建)

Question

我正在 SELECT 子句中创建一个临时列，如下所示:

SELECT *, 
       CASE WHEN a THEN 1 ELSE 0 END AS my_col 
FROM foo

现在我可以使用“my_col”访问和排序结果，即

SELECT *, 
       CASE WHEN a THEN 1 ELSE 0 END AS my_col 
FROM foo 
ORDER BY my_col

但是当我想要这样扩展列时

SELECT *, 
       CASE WHEN a THEN 1 ELSE 0 END AS my_col, 
       my_col * 5 AS my_col_2 
FROM foo

SQLite 生成“没有这样的列:my_col”。

那么如何使用临时列在查询中进一步使用呢？这可能吗？

Answer 1

您可以使用子查询:

SELECT X.my_col, X.my_col * 5 AS my_col_2
FROM (
     SELECT *, CASE WHEN a THEN 1 ELSE 0 END AS my_col FROM foo
     ) X
ORDER BY X.my_col

或者只是重复 case 语句:

SELECT *, CASE WHEN a THEN 1 ELSE 0 END AS my_col, CASE WHEN a THEN 1 ELSE 0 END * 5 AS my_col_2 FROM fo