Question

我正在尝试在查询中构建一个不同的字符串，除非其中一个值为NULL，否则它将起作用。我已经测试过删除了LOCATION_ADDR_LINE_2，查询就可以了。当我没有SELECT DISTINCT时，我发现LOCATION_ADDR_LINE_2值为NULL。即使NULL？

，如何在SELECT DISTINCT中收集这些值？

SELECT      DISTINCT(LOCATION_ADDR_LINE_1 + ', ' + LOCATION_ADDR_LINE_2 + ', ' + LOCATION_CITY + ', ' + LOCATION_WORK_STATE) AS Addresses
FROM        OracleReport
WHERE       (LOCATION_ADDR_LINE_1 LIKE '%1135 Auto%' OR LOCATION_ADDR_LINE_1 LIKE '%199 Easy%')

返回：

地址 NULL

SELECT      DISTINCT(LOCATION_ADDR_LINE_1 + ', ' + LOCATION_CITY + ', ' + LOCATION_WORK_STATE) AS Addresses
FROM        [OperationReport].[dbo].[OracleReport]
WHERE       (LOCATION_ADDR_LINE_1 LIKE '%1135 Auto%' OR LOCATION_ADDR_LINE_1 LIKE '%199 Easy%')

返回：

地址

1135自动...

189-199容易......

Answer 1

当值为NULL时，假设您不介意text,,text,...（空字符串）......

SELECT  DISTINCT(coalesce(LOCATION_ADDR_LINE_1,'') + ', ' +              
                 coalesce(LOCATION_ADDR_LINE_2,'') + ', ' + 
                 coalesce(LOCATION_CITY,'')  + ', ' + 
                 coalesce(LOCATION_WORK_STATE,'')) AS Addresses
FROM  OracleReport
WHERE (LOCATION_ADDR_LINE_1 LIKE '%1135 Auto%' 
    OR LOCATION_ADDR_LINE_1 LIKE '%199 Easy%')

Coalesce将获取第一个非null值并返回它。它需要一致的数据类型，并且一旦遇到系列中的第一个非空值，就会提前退出。（更多详情Oracle Differences between NVL and Coalesce）

SELECT DISTINCT在不需要时省略NULL值

1 个答案: