You can do one or the other of the following
------------ OPTION 1 ----------------
DECLARE @TEST as VARCHAR(30)
SET @TEST = '234'
INSERT INTO TABLE1(A, B)
SELECT TOP 1 @TEST, max(CAT) FROM TABLE2 where 1=1;
GO
--------------------------------------------
DECLARE @TEST as VARCHAR(30)
SET @TEST = '123'
INSERT INTO TABLE1(A, B)
SELECT TOP 1 @TEST, max(CAT) FROM TABLE2 where 1=1;
------------ OPTION 2 ----------------
DECLARE @TEST as VARCHAR(30)
SET @TEST = '234'
INSERT INTO TABLE1(A, B)
SELECT TOP 1 @TEST, max(CAT) FROM TABLE2 where 1=1;
--------------------------------------------
--DECLARE @TEST as VARCHAR(30)
SET @TEST = '123'
INSERT INTO TABLE1(A, B)
SELECT TOP 1 @TEST, max(CAT) FROM TABLE2 where 1=1;