SWAP Selected Rows in SQL Server - sql

Question

I am trying to swap the selected rows as a quick way for users to selected the opposite to what they have already selected.
For example:
Current Selection:
ID SelectedUID
------------------
1
2
3 CJ
4
5
SWAP Selection: (this is what I am trying to achieve)
ID SelectedUID
------------------
1 CJ
2 CJ
3
4 CJ
5 CJ
Is there a function or an easy way to do this in SQL Server?
EDIT
Would this be an appropriate Stored Procedure? I am receiving an error when I execute this.
CREATE PROCEDURE [dbo].[ProcSWAPSelections]
#FROMCLAUSE AS VARCHAR(8000),
#UPDATETABLE AS VARCHAR(50),
#GUID AS VARCHAR(3),
#WHERECLAUSE AS VARCHAR(8000)
AS
BEGIN
SET NOCOUNT ON;
DECLARE #SQL NVARCHAR(MAX);
SET #SQL = N'UPDATE ' + #UPDATETABLE + '
SET Selected' + #GUID + '.UID = CASE WHEN Selected' + #GUID + '.UID = #GUID
THEN NULL
ELSE #GUID
END
' + #FROMCLAUSE + '
' + #WHERECLAUSE + ';';
EXEC sp_executesql #sql, N'#FROMCLAUSE VARCHAR(8000), #UPDATETABLE VARCHAR(50), #GUID VARCHAR(3), #WHERECLAUSE VARCHAR(8000)', #FROMCLAUSE,#UPDATETABLE, #GUID, #WHERECLAUSE;
END

Answer 1

Another way would be to have a third table
Selections
ID Selection
1 NULL
2 CJ
Then in the swap table link to it, then you only need to switch in the selections table. Same number of operations, but only two records updated.

Answer 2

You can do this easily with 2 updates.
Update YourTable Set SelectedUID = 'SomeValueThatDoesntExist'
where SelectedID = 'CJ'
Update YourTable Set SelectedUID = 'CJ'
where SelectedID = 'SomeValueThatDoesntExist'

Answer 3

Assuming only 2 different values in the table in one update, which means you don't need a transaction to span multiple UPDATEs
UPDATE
SomeTable
SET
SelectedUID = CASE WHEN SelectedUID <> 'CJ' THEN 'CJ' ELSE '' END
or...
SelectedUID = CASE WHEN SelectedUID = 'CJ' THEN '' ELSE 'CJ' END
or...
SelectedUID = CASE WHEN SelectedUID = 'CJ' THEN NULL ELSE 'CJ' END

Answer 4

This function should help.
CREATE FUNCTION udf_SwapValues
(
#InputStr VARCHAR(5),
#ReplaceStr1 VARCHAR(5),
#ReplaceStr2 VARCHAR(5)
)
RETURNS VARCHAR(5)
AS
BEGIN
DECLARE #Return VARCHAR(5)
SELECT #Return = CASE
WHEN #InputStr = #ReplaceStr1 THEN #ReplaceStr2
WHEN #InputStr = #ReplaceStr2 THEN #ReplaceStr1
ELSE #InputStr
END
-- Return the result of the function
RETURN #Return
END
GO
USAGE:
DECLARE #table TABLE (ID INT,
SelectedUID VARCHAR(5))
INSERT INTO #table
VALUES (1, ''),
(2, ''),
(3, 'CJ'),
(4, ''),
(5, '')
SELECT ID,SelectedUID
FROM #table
--USAGE WITH SELECT
SELECT ID,
dbo.udf_SwapValues(SelectedUID, 'CJ', '')
FROM #table
--USAGE WITH UPDATE
UPDATE t
SET t.SelectedUID = dbo.udf_SwapValues(t.SelectedUID, 'CJ', '')
FROM #table t
SELECT *
FROM #table