Question

我写了一个SQL语句，但我无法得到理想的答案

Dim objDataAdapter As SqlDataAdapter = New SqlDataAdapter("SELECT FIBER.ID , LIST.STATION , LIST.CODE , FIBER.NUMBER , FIBER.OWNER , " _
+ " FIBER.KIND , FIBER.CORE_NUMBER , FIBER.LENGTH , FIBER.LOSS ,FIBER.COLOR , FIBER.CABINET , FIBER.R_NUMBER , NULL AS R_STATION , NULL AS R_CODE, FIBER.COMMENT FROM LIST " _
+ " INNER JOIN FIBER " _
 + " ON FIBER.NUMBER = LIST.NUM_CODE " _
 + " UNION  ALL" _
 + " SELECT FIBER.ID , NULL AS STATION , NULL AS CODE , FIBER.NUMBER , FIBER.OWNER , " _
+ " FIBER.KIND , FIBER.CORE_NUMBER , FIBER.LENGTH , FIBER.LOSS ,FIBER.COLOR , FIBER.CABINET , FIBER.R_NUMBER , LIST.STATION AS R_STATION , LIST.CODE AS R_CODE , FIBER.COMMENT FROM LIST " _
 + " INNER JOIN FIBER " _
+ " ON FIBER.R_NUMBER = LIST.NUM_CODE " _
, objConnection)

，答案是

！[我的回答必须是三条记录，但我找回了六条记录而且R_CODE，R_STATION被复制到以下三条记录中] [10]

感谢

Answer 1

而不是使用＆＃34; UNION ALL＆＃34; ，使用＆＃34; UNION＆＃34;。

因为UNION删除重复记录（结果中的所有列都相同），UNION ALL不会

SQL查询语句join和union

1 个答案: