optimize mysql table's physical storage

[tech user]

Hello,

My mysql table has been created for long time, it increases day by day,
and become huge.
Right now a full scan to the table for the first time is very slow.
So I was thinking to optimize it.
This table is stored in many non-sequential disk fragments I think.
I want to make this table to be stored in disk with the sequential
fragments.That will increase the scan speed.
Is there any tool to do it? Thanks in advance.

--ken


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help with a sql statement

[tech user]

hello,

I try to execute this sql in mysql shell,but got error as:

mysql select *  from (select uin,count(*) as dd from active_users where
date = date_add(curdate(),interval -30 day)  group by uin) where dd =3;

ERROR 1248 (42000): Every derived table must have its own alias

But I can execute the sql statement of select uin,count(*) as dd from
active_users where date = date_add(curdate(),interval -30 day)  group by
uin successfully.

How to fixup it? thanks!


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Re: help with a sql statement

[tech user]

 
 Add an alias for the subquery
 
   select * from ( select  ) my_alias where dd = 3;
 
 Better, use a having clause and eliminate the subquery.  Odds are it 
 will be more efficient in MySQL.
 

How to replace the original one with a having statement?
Thanks again.


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mysql connection problems

[tech user]

Hello members,

I have two mysqld run on the same host (redhat linux OS with 2.4 kernel).
the two mysqld are in different versions, one is 4.0.20,another is 5.0.45.

the mysql 4.0.20 uses /etc/my.cnf as its config file,listening on default
3306 port.
the mysql 5.0.45 uses /etc/mysql5.cnf as its config file,listening on 3307
port.

I start them on command line:

/usr/local/mysql/bin/mysqld_safe   # for mysql4
/opt/mysql5/bin/mysqld_safe --defaults-file=/etc/mysql5.cnf   # for
mysql5

All run fine.I didn't see exceptions in mysql's error logs.

But, when I try to connect to mysql5, with the command,

mysql -uroot -P3307 -h127.0.0.1

Sometime I login it successfully,but most time I can't. The connection
seems be blocked.

(I don't run any iptables or firewall on this host).

This let me really be confused. please help. Thanks!

--Ken


  
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