MERGE INTO demo.a AS T1 USING demo.b AS T2
ON T1.id = T2.id
WHEN MATCHED THEN UPDATE SET name = 'wf1'
WHEN NOT MATCHED THEN INSERT VALUES(T2.id,T2.name);

MERGE INTO demo.a AS T1 USING demo.b AS T2
ON T1.id = T2.id
WHEN MATCHED AND sex='male' THEN UPDATE SET name = 'wf1'
WHEN MATCHED AND sex='female' THEN UPDATE SET age = 10
WHEN NOT MATCHED AND age>10 THEN INSERT VALUES(T2.id,T2.name);