有条件地在没有存储过程的情况下在MySQL上提交事务

Question

I found their document said that the IF ELSE END IF is only supported in stored procedure.

MySQL supports the IF, CASE, ITERATE, LEAVE LOOP, WHILE, and REPEAT constructs for flow control within **stored programs**.

We tried and seem that it is not supported in running batch statements via cli.

To optimize the performance and reduce round trip, reading the ROW_COUNT() by an application is not considered. The best if mysql can take it in the speed of light.

How do I make it work without using any additional stored procedure? We tried to use WHERE ROW_COUNT() on every UPDATE to suspend the chain of updates if any one goes wrong; but it wont stop the transaction begin replicated even if nothing should be modified.

EDIT:

In short, how do I do

START TRANSACTION
UPDATE `table_a` SET a=1 WHERE id=1 AND addition=2;
UPDATE `table_b` SET a=1 WHERE id=1 AND another_rule=3;
IF UPDATE_COUNT() = 1 
THEN 
  COMMIT
ELSE
  ROLLBACK
END IF

In a crond schedule, without using stored procedure.

Answer 1

a work around if you don't want to use a stored procedure. it works fine for me

SET autocommit=0;
UPDATE table_a SET a=1 WHERE id=1 AND addition=2;
UPDATE table_b SET a=1 WHERE id=1 AND another_rule=3;
SET autocommit=IF(UPDATE_COUNT()=1,1,2);

autocommit will set to be 2 if not UPDATE_COUNT() = 1 and this will throw an exception
Variable 'autocommit' can't be set to the value of '2'
handle this exception and execute ROLLBACK;

Answer 2

I don't think what you want to do is possible, as is, without a stored procedure. Why are you averse to using a stored procedure? The only other way I can think of doing this atm, is to have a staging table that can trim your duplicates and then do your commit in one step.

Malks.