Question

Declare @cardNumber;
select name, address, 
 (select @cardNumber = select top 1 value from card cd
         inner join cardNotuse cdnu on cd.id = cdnu.cardId
         where cdnu.type = 'CreditCard'),
case when (@cardNumber = 1) then 'TopPriority'
     when (@cardNumber = 2) then 'SecondPriority'
     Else 'Normal' end as PriorityLeval

from customer

我不能以某种方式为@cardNumber分配价值。错误我有

＆＃39;＆＃39; =＆＃39;。
附近的语法不正确

我无法弄清楚为什么我无法使用这样的查询。

Answer 1

由于变量@cardNumber与customer表无关，您可以编写两个独立的查询AS：

Declare @cardNumber int;
set @cardNumber =  (SELECT  top 1 value 
                       from card cd
                       inner join cardNotuse cdnu on cd.id = cdnu.cardId
                       where cdnu.[type] = 'CreditCard')
select  name,
        address, 
        @cardNumber,
        case when (@cardNumber = 1) then 'TopPriority'
             when (@cardNumber = 2) then 'SecondPriority'
             Else 'Normal' end as PriorityLeval
from customer

Answer 2

请检查样本和评论。

Declare @cardNumber varchar(50) --here datatype missing

select name, address, 
        (--select @cardNumber =  --you can not do 2 thing in one select query, either set variable or get result, not both in a single query
        select top 1 value from card cd
         inner join cardNotuse cdnu on cd.id = cdnu.cardId
         where cdnu.type = 'CreditCard'
         ),
case when (@cardNumber = 1) then 'TopPriority'
     when (@cardNumber = 2) then 'SecondPriority'
     Else 'Normal' end as PriorityLeval

from customer 

--1. Either set statment to get value 
set @cardNumber =  
        (select top 1 value from card cd
         inner join cardNotuse cdnu on cd.id = cdnu.cardId
         where cdnu.type = 'CreditCard'
         )
--2.  or in select query you can set,but result always be a single value as you taken top 1 will not work for you.
select @cardNumber = --this gives error as top clause will not work
        top 1 value from card cd
         inner join cardNotuse cdnu on cd.id = cdnu.cardId
         where cdnu.type = 'CreditCard'

--This will work. If a single value there, it return a value. If more than one value, set last record.
select @cardNumber = value _Id from card cd
             inner join cardNotuse cdnu on cd.id = cdnu.cardId
             where cdnu.type = 'CreditCard'

在sql查询select中赋值变量

2 个答案: