Question

我有一张这样的表：

user | test_score
  a  |  50
  b  |  60

我需要的查询结果的列数是测试分数的1.5倍，然后是原始版本的差异。结果将是：

user | test_score | adjusted_test_score | test_score_diff
  a  |  50        |            75       |   25
  b  |  60        |            90       |   30

我试过的查询：

 SELECT
 user AS user,
 test_score AS test_score,
 (test_score * 1.5) AS adjusted_test_score,
 (adjusted_test_score - test_score) AS test_score_diff

返回'adjusted_test_score'列不存在的错误。

有没有办法在不进行连接的情况下引用此列？

Answer 1

尝试：

SELECT user, test_score, adjusted_test_score,
    (adjusted_test_score - test_score) AS test_score_diff
FROM (
    SELECT user, test_score, (test_score * 1.5) AS adjusted_test_score
    FROM source_table
)

或者您也可以这样做：

SELECT user, test_score, (test_score * 1.5) AS adjusted_test_score,
    ((test_score * 1.5) - test_score) AS test_score_diff
FROM source_table

Answer 2

为什么不重复自己？

选择用户AS用户， test_score AS test_score，（test_score * 1.5）AS adjusted_test_score，（（test_score * 1.5） - test_score）AS test_score_diff

MySQL - 在第二个动态列中引用动态列

2 个答案: