Thread: How to update an entire table by getting the values from another table?

Hi. I need to run an update query on a table, and need some help on
how to do it.


I have a table A(id integer primary key, prod_id integer, Y1 integer,
Y2 integer, ... Y14 integer)  and a table B (a integer references A, x
integer,unique(a) );

and now I should set (for each row in A)  prod_id to have the value
that is found in table B

How do I write a statement that does that?

In response to A B :
> Hi. I need to run an update query on a table, and need some help on
> how to do it.
>
>
> I have a table A(id integer primary key, prod_id integer, Y1 integer,
> Y2 integer, ... Y14 integer)  and a table B (a integer references A, x
> integer,unique(a) );
>
> and now I should set (for each row in A)  prod_id to have the value
> that is found in table B
>
> How do I write a statement that does that?

test=# select * from a;
 id | prod_id | y1
----+---------+----
  1 |         |
  2 |         |
  3 |         |
(3 rows)

test=*# select * from b;
 a | x
---+----
 1 | 10
 2 | 20
 3 | 30
(3 rows)

test=*# update a set prod_id = b.x from b where a.id=b.a;
UPDATE 3
test=*# select * from a;
 id | prod_id | y1
----+---------+----
  1 |      10 |
  2 |      20 |
  3 |      30 |
(3 rows)


HTH, Andreas
--
Andreas Kretschmer
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