Luk*_*zda 9 mysql sql sql-server postgresql
有一个简单的表:
CREATE TABLE tab AS
SELECT 1 AS t, 'G' AS company, 40 AS quote
UNION SELECT 2 , 'G', 60
UNION SELECT 3 , 'S', 60
UNION SELECT 4, 'S', 20;
并查询:
SELECT DISTINCT company, quote ,LAG(quote) OVER(PARTITION BY company ORDER BY t)
FROM tab;
输出 - 结果在RDBMS之间保持一致.
+---------+-------+------+
| company | quote | lag |
+---------+-------+------+
| G | 40 | null |
| S | 60 | null |
| G | 60 | 40 |
| S | 20 | 60 |
+---------+-------+------+
但是当我尝试进行一些计算时,我会得到不同的结果:
SELECT DISTINCT company, quote - LAG(quote) OVER(PARTITION BY company ORDER BY t)
FROM tab;
PostgreSQL/SQL Server/Oracle(正如我所料):
+---------+--------+
| company | result |
+---------+--------+
| G | null |
| G | 20 |
| S | null |
| S | -40 |
+---------+--------+
MariaDB的/ MySQL的:
+----------+--------+
| company | result |
+----------+--------+
| G | null |
| S | null |
+----------+--------+
- 从
- 上
- 加入
- 哪里
- 通过...分组
- WITH CUBE/ROLLUP
- HAVING
- 选择
- 不同
...
DISTINCT是的,SELECT所以正确的方法应该像PostgreSQL/SQL Server/Oracle.(是的,我知道我可以使用子查询/删除,DISTINCT但这不是问题的重点).
这种行为是错误还是正常工作(文档)？
绝对是 MySQL 和 MariaDB 中的错误。我已向两个数据库报告了该问题，并链接回 Stack Overflow 问题：