CASE expression syntax error SQL - sql

Question

I have researched everywhere but still can't seem to fix a simple error:
Running Microsoft SQL server:
UPDATE copyprogmaster
SET active =
CASE
WHEN active = 1 THEN active = 0
WHEN active = 0 THEN active = 1
ELSE active
END
WHERE source = 'Mass_Mail'
my error is :
Line 4: Incorrect syntax near '='.

Answer 1

Remove the = after the THEN, so:
UPDATE copyprogmaster
SET active =
CASE
WHEN active = 1 THEN 0
WHEN active = 0 THEN 1
ELSE active
END
WHERE source = 'Mass_Mail'
You already have active = after the SET on the second line.

Answer 2

You do not need to repeat "active =" after THEN
UPDATE copyprogmaster
SET active =
CASE
WHEN active = 1 THEN 0
WHEN active = 0 THEN 1
ELSE active
END
WHERE source = 'Mass_Mail'
Here's an example from the documentation at http://msdn.microsoft.com/en-us/library/ms181765.aspx
USE AdventureWorks2008R2;
GO
SELECT ProductNumber, Category =
CASE ProductLine
WHEN 'R' THEN 'Road'
WHEN 'M' THEN 'Mountain'
WHEN 'T' THEN 'Touring'
WHEN 'S' THEN 'Other sale items'
ELSE 'Not for sale'
END,
Name
FROM Production.Product
ORDER BY ProductNumber;
GO

Answer 3

Based on your query, I assume the active field is bit or int (assuming that int field has only values 0, 1, or NULL). In that case, I believe that you can write the query as following:
UPDATE dbo.copyprogmaster
SET active = active ^ 1
WHERE source = 'Mass_Mail'
Notice that the query can handle NULL values and also the rows #1, #4 and #6 in the screenshot are unchanged. Screenshot #1 shows table structure and screenshot #2 displays sample execution of the above query.
Hope that helps.
Screenshot #1:
Screenshot #2: