SQLite 3.27

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create table tab_1 (id int, name int, desc int);


create table tab_2 (id int, tab_id int, desc int);
insert into tab_1 values (1,1,1),
(2,2,2),
(5,5,5);
insert into tab_2 values (1,1,3),
(2,2,4);
select * from tab_1;


id
name
desc


1
1
1

2
2
2

5
5
5


select * from tab_2;


id
tab_id
desc


1
1
3

2
2
4


UPDATE 
      tab_1
SET desc = (SELECT desc
                  FROM tab_2
                  WHERE id = tab_1.id) 
where EXISTS (SELECT desc
                  FROM tab_2
                  WHERE id = tab_1.id)
select * from tab_1;


id
name
desc


1
1
3

2
2
4

5
5
5


UPDATE 
      tab_1
SET desc = (SELECT desc
                  FROM tab_2
                  WHERE id = tab_1.id) 
select * from tab_1;


id
name
desc


1
1
3

2
2
4

5
5
null