Thread: UPDATE command with FROM clause

Hi,

I have a query like this:

UPDATE chartsclub.secc_esp_votar_votos
SET svv_puntos = 0 FROM
(SELECT * FROM chartsclub.secc_esp_votar_votos AS tblVotos WHERE svv_sva_clave = 114 EXCEPT
       (SELECT DISTINCT ON (svv_fechareg) * FROM chartsclub.secc_esp_votar_votos AS tblVotos WHERE svv_sva_clave = 114 ORDER BY svv_fechareg))

Will the UPDATE command affect only (all) records generated by the SELECT clause in the FROM clause?

I suppose that, if I include a WHERE clause, the condition will be applied to the records obtained by the SELECT clause in the FROM clause. 

Is this correct?

My goal is to get a set of records from one table and update only such a set of records.

In this case, the set of records to be updated are those obtained by the SELECT command in the FROM clause.

As you can see, there is only one table involved but I added an alias to the SELECT statement in the FROM clause based on what I read in the documentation.

Best regards,

Jorge Maldonado

Libre de virus. www.avast.com

I'm not clear how the value of svv_fechareg affects which rows you don't want to update but I think all you need is something along the lines of

UPDATE chartsclub.secc_esp_votar_votos

set svv_puntos = 0

where svv_sva_clave =114

--here's where the purpose of svv_fechareg comes into play. if you have an explicit value(s) for it, apply that as "!=" or "not in (value, value)"

and svv_fechareg is not null