SQL Switch/Case in 'where' clause - sql

Question

I tried searching around, but I couldn't find anything that would help me out.
I'm trying to do this in SQL:
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
I know that I shouldn't have to put '= #locationID' at the end of each one, but I can't get the syntax even close to being correct. SQL keeps complaining about my '=' on the first WHEN line...
How can I do this?

Answer 1

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

Answer 2

without a case statement...
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)

Answer 3

Here you go.
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

Answer 4

I'd say this is an indicator of a flawed table structure. Perhaps the different location types should be separated in different tables, enabling you to do much richer querying and also avoid having superfluous columns around.
If you're unable to change the structure, something like the below might work:
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
)
And so forth... We can't change the structure of the query on the fly, but we can override it by making the predicates equal themselves out.
EDIT: The above suggestions are of course much better, just ignore mine.

Answer 5

The problem with this is that when the SQL engine goes to evaluate the expression, it checks the FROM portion to pull the proper tables, and then the WHERE portion to provide some base criteria, so it cannot properly evaluate a dynamic condition on which column to check against.
You can use a WHERE clause when you're checking the WHERE criteria in the predicate, such as
WHERE account_location = CASE #locationType
WHEN 'business' THEN 45
WHEN 'area' THEN 52
END
so in your particular case, you're going to need put the query into a stored procedure or create three separate queries.

Answer 6

OR operator can be alternative of case when in where condition
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

Answer 7

Please try this query.
Answer To above post:
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

Answer 8

Try this:
WHERE (
#smartLocationType IS NULL
OR account_location = (
CASE
WHEN #smartLocationType IS NOT NULL
THEN #smartLocationType
ELSE account_location
END
)
)

Answer 9

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

Answer 10

Try this query, it's very easy and useful: Its ready to execute!
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

Answer 11

In general you can manage case of different where conditions in this way
SELECT *
FROM viewWhatever
WHERE 1=(CASE <case column or variable>
WHEN '<value1>' THEN IIF(<where condition 1>,1,0)
WHEN '<value2>' THEN IIF(<where condition 2>,1,0)
ELSE IIF(<else condition>,1,0)
END)

Answer 12

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;

Answer 13

This worked for me.
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 )
The 4 digit century is determined by the rule, if the year is 50 or more, the century is 1900, otherwise 2000.
Given two 6 digit periods that mark the start and end period, like a quarter, return the rows that fall in that range.
-- 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

Answer 14

Try this query. Its very easy to understand:
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