Postgres 15

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CREATE tABLe groupL(custId int , aName TEXT) 

CREATE TABLE

CREATE TABLe aName (name1 TEXT, name2 TEXT)

CREATE TABLE

INSERT INTO aName VALUEs ('A','B')

INSERT 0 1

DO $$
DECLARE  
   custIdConstant integer := 10;  
BEGIN  
INSERT INTO groupL(custId, aName) 
SELECT custIdConstant, name1 FROM aName  WHERE NOT EXISTS (SELECT 1 FROM groupL WHERE custId = custIdConstant AND aName = name1);

INSERT INTO groupL(custId, aName) 
SELECT custIdConstant, name2 FROM aName WHERE NOT EXISTS (SELECT 1 FROM groupL WHERE custId = custIdConstant AND aName = name2);

END $$;

DO

SELECT * FROM groupL

custid
aname

10
A

10
B

SELECT 2

DO $$
DECLARE  
   custIdConstant integer := 10;  
BEGIN  
INSERT INTO groupL(custId, aName) 
SELECT custIdConstant, name1 FROM aName  WHERE NOT EXISTS (SELECT 1 FROM groupL WHERE custId = custIdConstant AND aName = name1);

INSERT INTO groupL(custId, aName) 
SELECT custIdConstant, name2 FROM aName WHERE NOT EXISTS (SELECT 1 FROM groupL WHERE custId = custIdConstant AND aName = name2);

END $$;

DO

SELECT * FROM groupL

custid
aname

10
A

10
B

SELECT 2