Augey,
Wednesday, May 08, 2002, 5:10:27 PM, you wrote:
AM> On one of my MySQL servers (Dell PowerEdge 800Mhz w/ 512MB RAM), I have
AM> a couple tables that have about 3 million records in each. However some
AM> of the records in the tables are duplicates of each other. Here is a
AM> query that should return the number of unique records for both tables:
AM> select count(*) from table1,table2 where table1.value != table2.value;
AM> However, this query has been running for more than 40 hours and still
AM> has not finished. Is this normal?
May be :) This is a very "hard" SQL statement. You will get in
result set full cartesian product of non-equal rows in your both tables,
i.e. (couple of millions rows)x(couple of millions rows) = ~number with 12 zeros :)
Re-write your statement with JOIN, look at:
http://www.mysql.com/doc/J/O/JOIN.html
AM> Thanks,
AM> Augey
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