Re: [SQL] SELECT DISTINCT too slow

Miroslav Šulc Thu, 01 Jun 2006 07:51:09 -0700

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?

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Re: [SQL] SELECT DISTINCT too slow

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