Re: Check to see if customer exist in second table. Help needs with psql

On 06/17/2018 12:19 PM, Rv02 wrote:
>
>
> psql
> I have two tables , table A and Table b. Table A has list of about 60000
> customers ID with all their details and Table B had customer is and age for
> over 500000 rows of customers.

I going to assume you meant Table B has customer ID and age above.
Does Table B have duplicate records for customer ID?
If so what I offer below might need to be revised.

>
> I need a query that will take a customer from table a and if that customer
> exists in table B then insert a yes in a new column in table a. Basically
> what I want to end up with in table a , is all the customers in this table
> and if they exist in table B then yes in a column. I.e the final result will
> be 60000 customers and additional column at the end with yes or no depending
> if they exist in table B.

For future reference there are examples below that cover this:

https://www.postgresql.org/docs/10/static/sql-update.html
"
UPDATE employees SET sales_count = sales_count + 1 FROM accounts
WHERE accounts.name = 'Acme Corporation'
AND employees.id = accounts.sales_person;
"

I would test on a dev database or at least use:

BEGIN;

...

COMMIT;

Untested:

BEGIN;
UPDATE a set new_column = 'f';
UPDATE
a
SET
new_column = 't'
FROM
b
WHERE
a.id = b.id;

ROLLBACK or COMMIT depending on outcome of above.

>
> Any help is appreciate it
>
>
>
> --
> Sent from: http://www.postgresql-archive.org/PostgreSQL-general-f1843780.html
>
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com