Question

您好我有下面的查询，我需要在class中使用if语句。

    Alter procedure dbo.GetName(@id int, @statusDate VARCHAR(50))
begin
select id, name 
from customer
where id = @id and
IF(@statusDate = 'Active')
    status > GetDate()
ELSE
    status < GetDate()
end

此状态是customer表中类型为date的列 @statusDate是我将要传递的参数（活动或非活动）如果在第二个'和'之后有效，我必须获得状态＆gt; GetDate（）今天的日期其他状态＆lt; GETDATE（）。

Answer 1

你不能在where子句中有if子句，但是你可以重构你在哪里做同样的事情。

试试这个

ALTER PROCEDURE dbo.GetName(@id int, @statusDate VARCHAR(50))
AS
SELECT id, name 
FROM customer
WHERE id = @id AND
(
   (@statusDate = 'Active' AND status > GetDate()) OR
   (@statusDate = 'Inactive' AND status < GetDate()) OR
   (@statusDate IS NULL)
)

Answer 2

我认为你可以摆脱if语句重构你的SQL：

SELECT id, name 
FROM  customer
WHERE id = @id and
(@statusDate = 'Active' and  status > GetDate()) or (@statusDate = 'Active' and  status < GetDate())

Answer 3

在SQL中，您将使用布尔OR运算符来实现相同的效果：

alter procedure dbo.GetName(@id int, @statusDate VARCHAR(50))
begin
select id, name 
from customer
where id = @id 
and (
    (@statusDate = 'Active' and status >= GetDate())
     or (@statusDate <> 'Active' and status < GetDate())
)

Answer 4

有时，像Gavin和Massimiliano这样的OR逻辑会导致性能下降。这导致人们尝试了许多选项，例如以下......

IF (@statusDate = 'Active')
  SELECT id, name FROM customer WHERE id = @id AND status > GetDate()
ELSE
  SELECT id, name FROM customer WHERE id = @id AND status < GetDate()

SELECT id, name FROM customer
WHERE id = @id
AND status > CASE WHEN @statusDate = 'Active' THEN  GetDate() ELSE         0 END
AND status < CASE WHEN @statusDate = 'Active' THEN '99991231' ELSE GetDate() END

SELECT id, name FROM customer WHERE id = @id AND status > GetDate() AND @statusDate = 'Active'
UNION ALL
SELECT id, name FROM customer WHERE id = @id AND status < GetDate() AND @statusDate = 'Inactive'

Answer 5

select id, name 
  from customer
  where id = @id 
        and 'T' = case 
                     when @statusDate = 'Active' then case 
                                                         when status > GetDate() then 'T'
                                                      end
                     else case 
                             when status < GetDate() then 'T'
                          end
                  end;

sql if语句在哪里

5 个答案: