Question

我有一个选择像这样：

SELECT * FROM (SELECT DISTICT COL1, COL2, COL3
               FROM view a WHERE conditions ....
              ) QUERY
WHERE CONDITIONS... LIMIT 20 OFFSET 0

我正在从Java执行此操作，我需要此查询返回唯一的ID。所以我尝试：

SELECT TRIM(CHAR(HEX(GENERATE_UNIQUE()))) AS GUID, QUERY.* FROM (SELECT DISTICT COL1, COL2, COL3
               FROM view a WHERE conditions ....
              ) QUERY
WHERE CONDITIONS... LIMIT 20 OFFSET 0

这个返回一个错误，告诉我我不能在那个地方使用这个功能。如果我尝试：

SELECT * FROM (SELECT DISTINCT TRIM(CHAR(HEX(GENERATE_UNIQUE()))) AS GUID, COL1, COL2, COL3
               FROM view a WHERE conditions ....
              ) QUERY
WHERE CONDITIONS... LIMIT 20 OFFSET 0

我有重复的行，因为这就像我执行查询时一样DISTINCT

有人知道这样做的方法吗？

我不知道DB2版本（我已经尝试过How to check db2 version中的所有解决方案）

Answer 1

如果可以使用数字id，那么仅使用row_number()：

SELECT CAST(ROW_NUMBER() OVER (ORDER BY COL1, COL2, COL3) as VARCHAR(255)) as unique_id,
       QUERY.*
FROM (SELECT DISTICT COL1, COL2, COL3
      FROM view a
      WHERE conditions ....
     ) QUERY
WHERE CONDITIONS...
LIMIT 20 OFFSET 0

在DB2中的Select上生成唯一ID

1 个答案: