sql - 'where' 子句中的 SQL 切换/大小写

Question

我尝试四处寻找，但找不到任何可以帮助我的东西。

我正在尝试在 SQL 中执行此操作：

declare @locationType varchar(50);
declare @locationID int;

SELECT column1, column2
FROM viewWhatever
WHERE
CASE @locationType
    WHEN 'location' THEN account_location = @locationID
    WHEN 'area' THEN xxx_location_area = @locationID
    WHEN 'division' THEN xxx_location_division = @locationID

我知道我不应该把'= @locationID'放在每一个的末尾，但我无法得到接近正确的语法。SQL 在第一行 WHEN 上一直抱怨我的“=”...

我怎样才能做到这一点？

score 206 · Accepted Answer

declare @locationType varchar(50);
declare @locationID int;

SELECT column1, column2
FROM viewWhatever
WHERE
@locationID = 
  CASE @locationType
      WHEN 'location' THEN account_location
      WHEN 'area' THEN xxx_location_area 
      WHEN 'division' THEN xxx_location_division 
  END

score 78 · Accepted Answer

没有案例陈述...

SELECT column1, column2
FROM viewWhatever
WHERE
    (@locationType = 'location' AND account_location = @locationID)
    OR
    (@locationType = 'area' AND xxx_location_area = @locationID)
    OR
    (@locationType = 'division' AND xxx_location_division = @locationID)

score 43 · Accepted Answer

干得好。

SELECT
   column1, 
   column2
FROM
   viewWhatever
WHERE
CASE 
    WHEN @locationType = 'location' AND account_location = @locationID THEN 1
    WHEN @locationType = 'area' AND xxx_location_area = @locationID THEN 1
    WHEN @locationType = 'division' AND xxx_location_division = @locationID THEN 1
    ELSE 0
END = 1

score 6 · Accepted Answer

我会说这是一个有缺陷的表结构的指标。也许不同的位置类型应该在不同的表中分开，使您能够进行更丰富的查询并避免周围有多余的列。

如果您无法更改结构，可能会使用以下方法：

SELECT
    *
FROM
    Test
WHERE
    Account_Location = (
        CASE LocationType
          WHEN 'location' THEN @locationID
          ELSE Account_Location
        END
    )
    AND
    Account_Location_Area = (
        CASE LocationType
          WHEN 'area' THEN @locationID
          ELSE Account_Location_Area
        END
    )

等等......我们不能动态地改变查询的结构，但是我们可以通过使谓词等于它们自己来覆盖它。

编辑：上述建议当然要好得多，请忽略我的建议。

score 6 · Accepted Answer

这样做的问题是，当 SQL 引擎去评估表达式时，它检查 FROM 部分以提取正确的表，然后检查 WHERE 部分以提供一些基本条件，因此它无法正确评估要在哪个列上的动态条件检查对照。

在检查谓词中的 WHERE 条件时，可以使用 WHERE 子句，例如

WHERE account_location = CASE @locationType
                              WHEN 'business' THEN 45
                              WHEN 'area' THEN 52
                         END

因此，在您的特定情况下，您将需要将查询放入存储过程或创建三个单独的查询。

score 6 · Accepted Answer

OR 运算符可以在 where 条件下替代 case

ALTER PROCEDURE [dbo].[RPT_340bClinicDrugInventorySummary]
    -- Add the parameters for the stored procedure here
     @ClinicId BIGINT = 0,
     @selecttype int,
     @selectedValue varchar (50)
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
SELECT
    drugstock_drugname.n_cur_bal,drugname.cdrugname,clinic.cclinicname

FROM drugstock_drugname
INNER JOIN drugname ON drugstock_drugname.drugnameid_FK = drugname.drugnameid_PK
INNER JOIN drugstock_drugndc ON drugname.drugnameid_PK = drugstock_drugndc.drugnameid_FK
INNER JOIN drugndc ON drugstock_drugndc.drugndcid_FK = drugndc.drugid_PK
LEFT JOIN clinic ON drugstock_drugname.clinicid_FK = clinic.clinicid_PK

WHERE   (@ClinicId = 0 AND 1 = 1)
    OR  (@ClinicId != 0 AND drugstock_drugname.clinicid_FK = @ClinicId)

    -- Alternative Case When You can use OR
    AND ((@selecttype = 1 AND 1 = 1)
    OR  (@selecttype = 2 AND drugname.drugnameid_PK = @selectedValue)
    OR  (@selecttype = 3 AND drugndc.drugid_PK = @selectedValue)
    OR  (@selecttype = 4 AND drugname.cdrugclass = 'C2')
    OR  (@selecttype = 5 AND LEFT(drugname.cdrugclass, 1) = 'C'))

ORDER BY clinic.cclinicname, drugname.cdrugname
END

score 3 · Accepted Answer

请尝试此查询。回复以上帖子：

select @msgID, account_id
    from viewMailAccountsHeirachy
    where 
    CASE @smartLocationType
        WHEN 'store' THEN account_location
        WHEN 'area' THEN xxx_location_area 
        WHEN 'division' THEN xxx_location_division 
        WHEN 'company' THEN xxx_location_company 
    END  = @smartLocation

score 2 · Accepted Answer

试试这个：

WHERE (
    @smartLocationType IS NULL 
    OR account_location = (
         CASE
            WHEN @smartLocationType IS NOT NULL 
                 THEN @smartLocationType
            ELSE account_location 
         END
    )
)

score 0 · Accepted Answer

CREATE PROCEDURE [dbo].[Temp_Proc_Select_City]
    @StateId INT
AS  
        BEGIN       
            SELECT * FROM tbl_City 
                WHERE 
                @StateID = CASE WHEN ISNULL(@StateId,0) = 0 THEN 0 ELSE StateId END ORDER BY CityName
        END

score 0 · Accepted Answer

试试这个查询，它非常简单有用：它可以执行了！

USE tempdb
GO

IF NOT OBJECT_ID('Tempdb..Contacts') IS NULL
    DROP TABLE Contacts

CREATE TABLE Contacts(ID INT, FirstName VARCHAR(100), LastName VARCHAR(100))
INSERT INTO Contacts (ID, FirstName, LastName)
SELECT 1, 'Omid', 'Karami'
UNION ALL
SELECT 2, 'Alen', 'Fars'
UNION ALL
SELECT 3, 'Sharon', 'b'
UNION ALL
SELECT 4, 'Poja', 'Kar'
UNION ALL
SELECT 5, 'Ryan', 'Lasr'
GO
 
DECLARE @FirstName VARCHAR(100)
SET @FirstName = 'Omid'
 
DECLARE @LastName VARCHAR(100)
SET @LastName = '' 
 
SELECT FirstName, LastName
FROM Contacts
WHERE  
    FirstName = CASE
    WHEN LEN(@FirstName) > 0 THEN  @FirstName 
    ELSE FirstName 
    END
AND
    LastName = CASE
    WHEN LEN(@LastName) > 0 THEN  @LastName 
    ELSE LastName
    END
GO

score -1 · Accepted Answer

Case Statement in SQL Server Example

Syntax

CASE [ expression ]

   WHEN condition_1 THEN result_1
   WHEN condition_2 THEN result_2
   ...
   WHEN condition_n THEN result_n

   ELSE result

END

Example

SELECT contact_id,
CASE website_id
  WHEN 1 THEN 'TechOnTheNet.com'
  WHEN 2 THEN 'CheckYourMath.com'
  ELSE 'BigActivities.com'
END
FROM contacts;

OR

SELECT contact_id,
CASE
  WHEN website_id = 1 THEN 'TechOnTheNet.com'
  WHEN website_id = 2 THEN 'CheckYourMath.com'
  ELSE 'BigActivities.com'
END
FROM contacts;

score -1 · Accepted Answer

这对我有用。


CREATE TABLE PER_CAL ( CAL_YEAR INT, CAL_PER INT )
INSERT INTO PER_CAL( CAL_YEAR, CAL_PER ) VALUES ( 20,1 ), ( 20,2 ), ( 20,3 ), ( 20,4 ), ( 20,5 ), ( 20,6 ), ( 20,7 ), ( 20,8 ), ( 20,9 ), ( 20,10 ), ( 20,11 ), ( 20,12 ), 
( 99,1 ), ( 99,2 ), ( 99,3 ), ( 99,4 ), ( 99,5 ), ( 99,6 ), ( 99,7 ), ( 99,8 ), ( 99,9 ), ( 99,10 ), ( 99,11 ), ( 99,12 )

4位世纪由规则确定，如果年份为50或更多，则世纪为1900，否则为2000。

给定两个标记开始和结束时间段的 6 位数时间段，例如四分之一，返回该范围内的行。


-- 1st quarter of 2020
SELECT * FROM PER_CAL WHERE (( CASE WHEN CAL_YEAR > 50 THEN 1900 ELSE 2000 END + CAL_YEAR ) * 100 + CAL_PER ) BETWEEN 202001 AND 202003
-- 4th quarter of 1999
SELECT * FROM PER_CAL WHERE (( CASE WHEN CAL_YEAR > 50 THEN 1900 ELSE 2000 END + CAL_YEAR ) * 100 + CAL_PER ) BETWEEN 199910 AND 199912

score -2 · Accepted Answer

试试这个查询。它很容易理解：

CREATE TABLE PersonsDetail(FirstName nvarchar(20), LastName nvarchar(20), GenderID int);
GO

INSERT INTO PersonsDetail VALUES(N'Gourav', N'Bhatia', 2),
              (N'Ramesh', N'Kumar', 1),
              (N'Ram', N'Lal', 2),
              (N'Sunil', N'Kumar', 3),
              (N'Sunny', N'Sehgal', 1),
              (N'Malkeet', N'Shaoul', 3),
              (N'Jassy', N'Sohal', 2);
GO

SELECT FirstName, LastName, Gender =
    CASE GenderID
    WHEN 1 THEN 'Male'
    WHEN 2 THEN 'Female'
    ELSE 'Unknown'
    END
FROM PersonsDetail

sql - 'where' 子句中的 SQL 切换/大小写

13 回答 13

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