Postgres 17

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create table A (id integer not null primary key, acol varchar(20));

create table B (id integer not null primary key, bcol varchar(20));

create table C (id integer not null primary key, ccol varchar(20));

insert into A values (1,'a'), (2,'a'), (100,'a');

insert into B values (1,'b'), (200,'b');

insert into C values (1,'c'), (2,'c'), (3,'c'), (300,'c');

CREATE TABLE



CREATE TABLE



CREATE TABLE



INSERT 0 3



INSERT 0 2



INSERT 0 4


select * from
  (A left join B on A.id=B.id) left join C on A.id=C.id;


id
acol
id
bcol
id
ccol


1
a
1
b
1
c

2
a
null
null
2
c

100
a
null
null
null
null



SELECT 3


select * from 
  A left join (B left join C on B.id=C.id) on A.id=B.id;


id
acol
id
bcol
id
ccol


1
a
1
b
1
c

2
a
null
null
null
null

100
a
null
null
null
null



SELECT 3

id	acol	id	bcol	id	ccol
1	a	1	b	1	c
2	a	null	null	null	null
100	a	null	null	null	null