JOIN 中的案例语句

Question

我有这个问题：

Select b.building_pk, bil.building_fk, bil.BillingAccountStatus_fk, b.ACTL_TNT_CT 
From [DB].[Schema].Building b (nolock)
left Join [DB].[Schema].Billing bil (nolock) on bil.building_fk = b.building_pk
join ##GlobalTempTable1 tt (nolock) on tt.Building_fk = b.building_pk
Order by b.building_pk; 

它工作正常。但我想在bil.building_fk 和bil.BillingAccountStatus_fk 列的结果集中覆盖NULLs，因为并非Billing tbl 中的所有内容都存在于构建表中。

因此在下面编写了以下查询，但收到此错误消息。

消息 102，级别 15，状态 1，第 7 行 '=' 附近的语法不正确。

请帮忙。

SELECT b.building_pk, bil.building_fk As [BLD Key from Billing], bil.BillingAccountStatus_fk, b.ACTL_TNT_CT As [ActualTenantCount] 
FROM [DB].[Schema].Building b (nolock)
join ##GlobalTempTable1 tt (nolock) ON tt.Building_fk = b.building_pk
left Join [DB].[Schema].Billing bil (nolock) ON
CASE
    WHEN bil.building_fk IS NOT NULL 
        THEN bil.building_fk = b.building_pk AND bil.BillingAccountStatus_fk = bil.BillingAccountStatus_fk
    WHEN bil.building_fk IS NULL
        THEN bil.building_fk = NULL AND bil.BillingAccountStatus_fk = 'Not in Billing'
    END
ORDER BY b.building_pk;

Answer 1

很难说你想做什么，因为这是非常错误的。不过，我认为，您希望保持 FROM 不变，并将 CASE 语句添加到 SELECT 中。

Select b.building_pk, CASE WHEN bil.Building_fk IS NULL THEN 'Not in Billing' ELSE bil.building_fk END as building_fk, bil.BillingAccountStatus_fk, b.ACTL_TNT_CT 
From [DB].[Schema].Building b (nolock)
left Join [DB].[Schema].Billing bil (nolock) on bil.building_fk = b.building_pk
join ##GlobalTempTable1 tt (nolock) on tt.Building_fk = b.building_pk
Order by b.building_pk; 

或者，更好的是，在这里使用COALESCE()：

Select b.building_pk, COALESCE(bil.Building_fk,'Not in Billing') as building_fk, bil.BillingAccountStatus_fk, b.ACTL_TNT_CT 
From [DB].[Schema].Building b (nolock)
left Join [DB].[Schema].Billing bil (nolock) on bil.building_fk = b.building_pk
join ##GlobalTempTable1 tt (nolock) on tt.Building_fk = b.building_pk
Order by b.building_pk; 

Answer 2

我猜你正在尝试做这样的事情：

SELECT b.building_pk, bil.building_fk As [BLD Key from Billing], bil.BillingAccountStatus_fk, b.ACTL_TNT_CT As [ActualTenantCount] 
FROM [DB].[Schema].Building b (nolock)
join ##GlobalTempTable1 tt (nolock) ON tt.Building_fk = b.building_pk
left Join [DB].[Schema].Billing bil (nolock) ON
    (bil.building_fk IS NOT NULL AND 
        (bil.building_fk = b.building_pk AND bil.BillingAccountStatus_fk = bil.BillingAccountStatus_fk))
    OR (bil.building_fk IS NULL AND
        (bil.building_fk = NULL AND bil.BillingAccountStatus_fk = 'Not in Billing'))
ORDER BY b.building_pk;

我将把 nolock 的错误用法留到另一天 ...

Answer 3

CASE 表达式不能用于设置用于JOIN 的条件，它们可以用于JOIN 条件中比较运算符的任一侧，但我认为您不需要，我认为您只需要在您的SELECT 中添加一个LEFT JOIN 和一个COALESCE()：

SELECT b.building_pk
     , bil.building_fk As [BLD Key from Billing]
     , COALESCE(bil.BillingAccountStatus_fk,'Not in Billing')
     , b.ACTL_TNT_CT As [ActualTenantCount] 
FROM [DB].[Schema].Building b 
join ##GlobalTempTable1 tt 
   ON tt.Building_fk = b.building_pk
left Join [DB].[Schema].Billing bil 
   ON bil.building_fk = b.building_pk
ORDER BY b.building_pk;

编辑：注意到BillingAccountStatus_fk 双方都来自bil，因此将其从JOIN 标准中删除。