where子句中的case語句 - SQL Server
[英]case statement in where clause - SQL Server
I'm trying to add a case or if statement in the where clause of my SQL query.
I have a table of journey times with a start and end date, and a boolean field for each day to signify where the journey happens on that day. Here is what I have so far, but I'm getting incorrect syntax errors:
我正在嘗試在我的SQL查詢的where子句中添加case或if語句。我有一個旅程時間表，包含開始和結束日期，每天都有一個布爾字段表示當天的旅程。這是我到目前為止，但我得到不正確的語法錯誤：
declare @date datetime
set @Date = '05/04/2012'
declare @day nvarchar(50)
set @day = 'Monday'
Select * From Times
WHERE (StartDate <= @Date) AND (EndDate >= @Date)
CASE WHEN @day = 'Monday' THEN
AND (Monday = 1)
WHEN @day = 'Tuesday' THEN
AND (Tuesday = 1)
ELSE
AND (Wednesday = 1)
END
3 个解决方案
#1
47
You don't need case in the where statement, just use parentheses and or:
你在where語句中不需要case，只需使用括號和or：
Select * From Times
WHERE StartDate <= @Date AND EndDate >= @Date
AND (
(@day = 'Monday' AND Monday = 1)
OR (@day = 'Tuesday' AND Tuesday = 1)
OR Wednesday = 1
)
Additionally, your syntax is wrong for a case. It doesn't append things to the string--it returns a single value. You'd want something like this, if you were actually going to use a case statement (which you shouldn't):
此外，您的語法錯誤的情況。它不會向字符串附加內容 - 它返回單個值。如果你真的要使用case語句（你不應該這樣），你會想要這樣的東西：
Select * From Times
WHERE (StartDate <= @Date) AND (EndDate >= @Date)
AND 1 = CASE WHEN @day = 'Monday' THEN Monday
WHEN @day = 'Tuesday' THEN Tuesday
ELSE Wednesday
END
And just for an extra umph, you can use the between operator for your date:
只需要額外的umph，您可以使用Between運算符作為您的日期：
where @Date between StartDate and EndDate
Making your final query:
進行最終查詢：
select
*
from
Times
where
@Date between StartDate and EndDate
and (
(@day = 'Monday' and Monday = 1)
or (@day = 'Tuesday' and Tuesday = 1)
or Wednesday = 1
)
#2
5
simply do the select:
只需選擇：
Select * From Times
WHERE (StartDate <= @Date) AND (EndDate >= @Date) AND
((@day = 'Monday' AND (Monday = 1))
OR (@day = 'Tuesday' AND (Tuesday = 1))
OR (Wednesday = 1))
#3
1
A CASE statement is an expression, just like a boolean comparison. That means the 'AND' needs to go before the 'CASE' statement, not within it.:
CASE語句是一個表達式，就像布爾比較一樣。這意味着'AND'需要在'CASE'語句之前，而不是在其中：
Select * From Times
WHERE (StartDate <= @Date) AND (EndDate >= @Date)
AND -- Added the "AND" here
CASE WHEN @day = 'Monday' THEN (Monday = 1) -- Removed "AND"
WHEN @day = 'Tuesday' THEN (Tuesday = 1) -- Removed "AND"
ELSE AND (Wednesday = 1)
END
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