UNION OF IF CONDITION QUERIES

IF(I=I && J==J)
BEGIN
SELECT ID,* FROM TABLE1 UNION SELECT * FROM TABLE2 GROUP BY id
END

else
begin

IF(J=J)
BEGIN
SELECT ID,* FROM TABLE1 GROUPBY ID
END


else
begin
IF(I=I)
BEGIN
SELECT ID,* FROM TABLE2 GROUPBY ID
END
end

end


But be sure that table1 and table2 have equal number of expressions in it.

If condition and union both are required then that can be done as shown below:


IF (J=J) THEN
IF (I=I) THEN
SELECT ID,* FROM TABLE1
UNION
SELECT ID,* FROM TABLE2
Group by ID

That is you can use nested if and then union those two queries required to perform union function. All the best.

why don't try temp table, such as:

IF(J=J)
BEGIN
SELECT ID,* INTO #TEMPTBL1 FROM TABLE1
END

IF(I=I)
BEGIN
SELECT ID,* INTO #TEMPTBL2 FROM TABLE2
END

SELECT * FROM #TEMPTBL1
UNION
SELECT * FROM #TEMPTBL2