mysql - 当我们需要使用upper（列名）排序时，如何在oracle中使用order by子句和union子句？

Question

以下查询给出错误：

SELECT DISTINCT dealer_state
FROM A
WHERE country='SS' 
UNION
SELECT DISTINCT dealer_state
FROM B
WHERE country='SS'
ORDER BY upper(dealer_state)

如何使用upper（column）按子句排序？

Answer 1

假设您的查询给出的“错误”是它没有像您预期的那样对记录中的记录进行排序B，A您需要使UNION查询成为执行排序的子查询：

SELECT dealer_state FROM (
    SELECT dealer_state FROM A WHERE country='SS' 
  UNION
    SELECT dealer_state FROM B WHERE country='SS'
) t
ORDER BY upper(dealer_state)

Answer 2

DISTINCT和中最左边的表达式ORDER BY必须匹配。

最简单的方法是执行以下操作：

SELECT dds FROM (
    SELECT DISTINCT dealer_state AS dds FROM A
     WHERE country='SS'
    UNION
    SELECT DISTINCT dealer_state AS dds FROM B
     WHERE country='SS') AS d
ORDER BY upper(dds);