如何使用SQL中的where exists？

这就是我的问题——写一个select语句，从gla表返回两列：acc.num和acc.descrp。结果应具有从未使用过与inv.line表的完全外部联接的帐号。从未使用过的部分让我感到困惑，我的代码给了我缺少的关键字错误。有什么想法吗

select Account_Number, Account_Description
 from GENERAL_LEDGER_ACCOUNTS gla full join INVOICE_LINE_ITEMS inv
where not exists
(select *
  from 
  where inv.ACCOUNT_NUMBER= Gla.ACCOUNT_NUMBER
 )
   order by Account_number

---

我是MSSQL开发人员，但基于此示例

你会变成

select Account_Number, Account_Description
 from GENERAL_LEDGER_ACCOUNTS gla 
 -- when you use join, you need to specify the relation between which column and which column this join
 full join INVOICE_LINE_ITEMS inv on gla.ACCOUNT_NUMBER= inv.ACCOUNT_NUMBER
where not exists
(select 1
  from 
  where inv.ACCOUNT_NUMBER= Gla.ACCOUNT_NUMBER
 )

但是从你的问题来看，你想要所有没有在任何发票中使用的账户，你可以通过简单的方式做到这一点

select Account_Number, Account_Description
 from GENERAL_LEDGER_ACCOUNTS gla 
where not exists
(select 1
  from INVOICE_LINE_ITEMS inv
  where inv.ACCOUNT_NUMBER= Gla.ACCOUNT_NUMBER
 )

希望这将帮助您

您可以使用not inMSSQL子句来获取此信息

select Account_Number, Account_Description
from GENERAL_LEDGER_ACCOUNTS 
where ACCOUNT_NUMBER not in(select ACCOUNT_NUMBER from INVOICE_LINE_ITEMS)

---

这相当于不存在查询。

我不确定您是否清楚地了解您的需求，您为什么不使用该查询：

select gla.Account_Number, gla.Account_Description
--     ^^^^                ^^^^
--      specify the table alias in case of duplicate columns

from GENERAL_LEDGER_ACCOUNTS gla full join INVOICE_LINE_ITEMS inv
--                               ^^^^^^^^^
--                            ??? see note below

on inv.ACCOUNT_NUMBER = Gla.ACCOUNT_NUMBER
-- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
--               join clause

where inv.ACCOUNT_NUMBER IS NULL
--    ^^^^^^^^^^^^^^^^^^^^^^^^^^
-- as this is a full outer join, some rows in `gla`
-- might not have a matching row in `inv`
-- This will keep only those rows

order by Account_number

---

另外，根据你的描述，我想说你只需要一个左连接，而不是一个完整的外部连接

我想你需要在gla中的哪一列和inv中的哪一列之间加入to join on关键字。你如何向我展示如何使用上面的代码，请感谢@HadiHassanWhat's outer join gla to inv on？您需要使用ON子句来表示这一点，正如@Hadi已经指出的那样