Postgres 9.6

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CREATE TABLE table1 (
    id_table1 serial,
    columnA text,
    columnB text
);

CREATE TABLE table2 (
    id_table2 serial,
    columnC text,
    columnD text,
    id_table1 int
);

INSERT INTO table1 (columnA, columnB) VALUES 
('a', 'a'),
('a', 'b');

INSERT INTO table2 (columnC, columnD, id_table1) VALUES 
('a', 'b', 1),
('a', 'b', 1),
('a', 'b', 2),
('a', 'a', 2);

SELECT * FROM table1;
2 rows affected

4 rows affected



id_table1
columna
columnb


1
a
a

2
a
b


SELECT * FROM table2;


id_table2
columnc
columnd
id_table1


1
a
b
1

2
a
b
1

3
a
b
2

4
a
a
2


WITH insert1 AS (
    INSERT INTO table1 (columnA, columnB) VALUES
    ('x', 'y')
    RETURNING id_table1
)
INSERT INTO table2 (columnC, columnD, id_table1) VALUES
('z', 'a', (SELECT id_table1 FROM insert1));

SELECT * FROM table1;
1 rows affected



id_table1
columna
columnb


1
a
a

2
a
b

3
x
y


SELECT * FROM table2


id_table2
columnc
columnd
id_table1


1
a
b
1

2
a
b
1

3
a
b
2

4
a
a
2

5
z
a
3