How to cancel auto commit?

I　want to commit manually.How can i do that not auto commit the transaction.I want to test the mysql transaction and isolation like:
begin;
select count(*) from beiker_region_property
where id=10100100 for update;
commit;

thanks

first,

SET @@session.autocommit = 0;

thanks jfalch for your replay,but not work for me:
I try your solution:
set @@session.autocommit=0;
begin;
select count(*) from beiker_region_property
where id=10100100 for update;
commit;

not working,just get the executed result without executing the commit.

1) try set @@autocommit = 0;

2) what server version are you using ?

3) you know that autocommit has an effect only if the storage engine used for your table(s) supports transactions ? InnoDB does (as well as ndbcluster, PBXT, SolidDB); MyISAM does NOT, so setting autocommit (or anything else) will not have an effect with MyISAM.

server version:5.1.48-log
storage engine:InnoDB

HeidiSQL does not have a GUI for it but you can always run the appropriate SQL commands:

start transaction;
select count(*) from beiker_region_property
where id=10100100 for update;

... and finally:

commit;

... or:

rollback;

what is returned by
SELECT @@GLOBAL.tx_isolation, @@tx_isolation;
?

@kalvaro i tried your solution,not work.
1.

start transaction;
select count(*) from beiker_region_property
where id=10100100 for update;

and then run above in another query tab
2.

start transaction;
select count(*) from beiker_region_property
where id=10100100 for update;

In the second query,i get the query result immediately,but i did not run commit command.

@jfalch Run

SELECT @@GLOBAL.tx_isolation, @@tx_isolation

get:

REPEATABLE-READ REPEATABLE-READ

Er, you cannot nest transactions in MySQL. If you attempt to start a new one, MySQL will make an implicit commit. Whatever, the

SET @@session.autocommit = 0;

tecnique jfalch explained should do the trick, if you are using InnoDB tables. There's no way to get transactions with MyISAM!

heidisql do not support start transaction manually? anyone else has suggestion?

Please, check again to what value @@autocommit is set:

set @@autocommit:=0;
select @@autocommit;

@anse

set @@autocommit:=0;
select @@autocommit;

get:
[b]0[/b]

Where can i set the autocommit to false in the heidisql? It seemed user can set autocommit to false in the heidisql in the previous version.But i can not find the settings anywhere now.

You just did it, by firing "set @@autocommit:=0", successfully, as your reply reveals. That should do it, on InnoDB tables, not on MyISAM tables, as said above.

Thanks ansgar!

Please, check again to what value @@autocommit is set:

set @@autocommit:=0;
select @@autocommit;

worked perfectly.