DB2 Merge

Hello All,

I'm have 2 tables Tb1 and Tb2.
Tb1 columns:
C1, C2, C3, C4, C5, C6, C7
k1 A, 1, 2, B, 3, 4

Tb2 columns:
C1, C2, C3, C4
K1, A, 1, 2
K1, B, 3, 4

Tb2 is pivoted. So requirement is i want to update from Tb1 if the key values are available in Tb2 and want to insert if the key values are not available in Tb2.

For that i'm using Merge: I can able to do update but insert is failing.

Could anybody pl help me here.

MERGE INTO Tb1 AS a
USING (SELECT * FROM Tb2) AS b ON (a.c1 = b.c1) AND a.c2 IN (b.c2, b.c5)
WHEN MATCHED AND (a.c2 = b.c2) THEN
UPDATE SET (a.c3,a.c4) = (b.c3,b.c4)

WHEN MATCHED AND (a.c2 = b.c5) THEN
UPDATE SET (a.c3,a.c4) = (b.c6,b.c7)

WHEN NOT MATCHED THEN
#Here i'm spliting Tb1 record into 2 records to insert into Tb2
INSERT SELECT c1, c2, c3, c4 FROM Tb1 WHERE c1=b.c1
UNION ALL
SELECT c1, c5, c6, c7 FROM Tb1 WHERE c1=b.c1;

But in Db2 we can do multiple inserts with single Insert statement like below. The same statement is not working in Merge s

INSERT into Tb2
SELECT c1, c2, c3, c4 FROM Tb1 WHERE c1='K1' AND c2='A'
UNION ALL
SELECT c1, c5, c6, c7 FROM Tb1 WHERE c1='K1' AND c5='B';