Question

我试图根据列和WHERE IN子句加入两个表。

SELECT DISTINCT
    t1.document_num, t2.file_name 
FROM 
    infocard_1 AS t1 
INNER JOIN 
    web_pub_subfile AS t2 on t1.info_card_id = t2.info_card_id
WHERE 
    lower(t1.vault_name) LIKE N'%su-spec-release%' AND 
    t2.file_name = 
       CASE 
          WHEN t2.file_name IN ('00350.dwg', '00924.dwg', '00960.dwg', '00973.dwg') 
             THEN t2.file_name
             ELSE NULL
       END

我以这种格式获得输出

document_num    file_name
-------------------------
SU-SH3A081      00960.DWG
SU-SH3A148      00973.DWG

但我想得到

document_num    file_name
-------------------------
null            00350.dwg
null            00924.dwg
SU-SH3A081      00960.DWG
SU-SH3A148      00973.DWG

有什么方法可以实现这个目标吗？请帮我。

Answer 1

您需要的是RIGHT JOIN而不是INNER JOIN。详细了解JOINS here的类型。

Answer 2

试试这个：

SELECT distinct t1.document_num,t2.file_name 
FROM web_pub_subfile AS t2  
LEFT JOIN infocard_1 AS t1 on t1.info_card_id = t2.info_card_id AND 
                              lower(t1.vault_name) LIKE N'%su-spec-release%'
WHERE  t2.file_name IN ('00350.dwg','00924.dwg','00960.dwg','00973.dwg')

Answer 3

为什么CASE中有WHERE个表达式？这使得阅读非常困难。必要时使用AND或OR和括号来构建WHERE子句。您的条款只是转换为：

WHERE lower(t1.vault_name) LIKE N'%su-spec-release%' 
AND t2.file_name IN ('00350.dwg','00924.dwg','00960.dwg','00973.dwg')

要从表中获取记录，即使它们在另一个表中没有匹配项，您也要加入另一个表。

SELECT DISTINCT ic.document_num, wps.file_name 
FROM web_pub_subfile wps
LEFT JOIN infocard_1 ic ON ic.info_card_id = wps.info_card_id
                        AND lower(ic.vault_name) LIKE N'%su-spec-release%'
WHERE wps.file_name IN ('00350.dwg','00924.dwg','00960.dwg','00973.dwg');

我用可读的东西替换了你的别名。

如果在SQL中的WHERE CLAUSE中找不到某些值，则显示NULL

3 个答案: