Re: [SQL] SELECT DISTINCT too slow

[Miroslav Šulc]

Well, "key" is not primary key from another table. It is just a column in pair "key" => "value". The structure of the table is this: Id (primary key) MRTPContactId (id of contact from table MRTPContact) Key (key from pair key => value) Value (value from pair key => value) So I want the get the list of keys used in the table. Miroslav Šulc Alvaro Herrera napsal(a): Miroslav ?ulc wrote: Hello, I have a table with cca 400,000 rows. The table contains column "key" of varchar(20) type containing 10 distinct values. I want to get out what distinct values are present in the column. I use this simple query, which is very slow: SELECT DISTINCT Key FROM MRTPContactValue You could get the universe of values from the table where this is a primary key, and use an IN clause (which apparently is more efficient than an EXISTS in some cases, but try that too) to search for values that exist in the MRTPContactValue table. I assume you do have the other table, don't you?

begin:vcard
fn;quoted-printable:Miroslav =C5=A0ulc
n;quoted-printable:=C5=A0ulc;Miroslav
org:StartNet s.r.o.
adr;quoted-printable;quoted-printable:;;Schodov=C3=A1 309/10;Praha 5;;150 00;=C4=8Cesk=C3=A1 republika
email;internet:[EMAIL PROTECTED]
tel;cell:+420 603 711 413
x-mozilla-html:TRUE
url:http://www.startnet.cz
version:2.1
end:vcard


---------------------------(end of broadcast)---------------------------
TIP 5: don't forget to increase your free space map settings