Question

我的查询有问题，例如我可以检索这些记录：

SELECT 
l.*, 
ll.f_cocacola as cocacola, 
 le.name AS deposit, 
 lp.price
FROM 
 KPC AS l, 
 KPC_cocacola AS ll, 
 KPC_deposit AS le, 
 KPC_price AS lp 
WHERE 
l.cod_deposit = le.id_deposit 
AND l.code = ll.code
AND lp.code = l.code
AND l.code_deposit = '002365'

但现在我需要在另一个表-intranet中包含另一个日期 - 其中包含 code 和 url 字段，然后需要从此表中显示 url 字段..请记住，该关系位于代码字段。

所以我以这种方式更改查询：

SELECT l.*,ll.f_cocacola as cocacola, le.name AS deposit, 
lp.price, lintranet.url 
FROM tableX AS l, intranet_cocacola AS ll, tableX_deposit AS le, 
tableX_price AS lp, 
tableX_intranet as lintranet 
WHERE l.code_deposit = le.id_deposit
AND l.code = ll.code
AND lp.code = l.code 
AND l.code = lintranet.code
AND l.code_deposit = '456852147'

但问题是某些记录没有 url ，如果不存在 url ，则此查询不会向我显示记录..我需要的是即使没有与记录关联的 url 我也希望看到该记录，谢谢

Answer 1

使用ANSI连接语法重写您的查询并使用LEFT JOIN：

SELECT  l.*, ll.f_cocacola as cocacola, le.name AS deposit, 
        lp.price, lintranet.url 
FROM    tableX AS l,
JOIN    intranet_cocacola AS ll
ON      ll.code = l.code
JOIN    tableX_deposit AS le
ON      le.id_deposit = l.code_deposit
JOIN    tableX_price AS lp
ON      lp.code = l.code
LEFT JOIN
        tableX_intranet as lintranet
ON      lintranet.code = l.code
WHERE   l.code_deposit = '456852147'

Answer 2

改为使用LEFT JOIN：

SELECT l.*,ll.f_cocacola as cocacola, le.name AS deposit, 
lp.price, lintranet.url 
FROM tableX AS l, intranet_cocacola AS ll, tableX_deposit AS le, 
tableX_price AS lp
LEFT JOIN tableX_intranet as lintranet ON l.code = lintranet.code -- <<<<<
WHERE l.code_deposit = le.id_deposit
AND l.code = ll.code
AND lp.code = l.code 
AND l.code_deposit = '456852147'

PS：我个人更喜欢显式INNER JOIN，而不是使用逗号分隔的表枚举加入。因为它可以更好地了解查询的作用

Answer 3

我意识到你已经有了答案，但我看到你的问题是通过Oracle数据库进行的...虽然我认为LEFT JOIN有效，因为它是标准的SQL，Oracle有它自己的版本，所以你可以看到这个相同的查询写成如下：

SELECT l.*,ll.f_cocacola as cocacola, le.name AS deposit, lp.price, lintranet.url 
  FROM tableX AS l, intranet_cocacola AS ll, tableX_deposit AS le, tableX_price AS lp, tableX_intranet as lintranet
 WHERE l.code_deposit = le.id_deposit
   AND l.code = ll.code
   AND lp.code = l.code 
   AND l.code_deposit = '456852147'
   AND l.code = lintranet.code(+)  //<-- this is how a left/right join is written
                                   //on Oracle's SQL, you add "(+)" next to the 
                                   //field of the table that may not have 
                                   //matching records.

不显示所有记录的SQL查询

3 个答案: