"A. Brandic" wrote:
>
> Hi!
>
> I've got a problem with MySql and I'm not sure if it is a bug or my
> fault. I'm running MySql 3.22.21
> on Alpha 800 with Unix 4.0 on it and MySql was installed as Binary version.
>
> I've created three test tables each containing just over 15000 records in
> 14 columns.
> If I do a simple query such as :
> mysql> select Universe.Surname from Universe, TestTable where
> -> ID=AdmissionNo;
>
> ID is unique for TestTable and it is integer(9) Primary Key and
> auto_increment and
> AdmissionNo is unique for Universe and it is integer(9) Primary Key and
> auto_increment as well.
>
> This executes in 1.05 secs with no probs.
>
> But when I do a similar query:
> mysql> select Universe.Surname from Universe, TestTable, Streams where
> -> ID=AdmissionNo;
>
> Still ID and AdmissionNo are Unique for their tables and do not appear in
> any other table but this time
> I've inserted Streams table which is not used at all.
> Well this time after 2min the following is displayed
>
> mysql: Out of memory (Needed 8160 bytes)
> ERROR 2008: MySQL client run out of memory
>
> and also it disconnects me from the database that I was usinq and I have
> to logi in again.
Well, I find the error message confusing. But I can explain the
problem...
Your query wasn't useful. Adding a table to a select, and not
specifying any conditions, will do a cartesian product. So if your
original query returns N rows, and your Streams table has M rows, then
this is going to return MN rows.
Which could be a very big number..
Jules
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