Updating trigger mysql
Updating trigger mysql
Bill explores the basic syntax, using SQL statements to create, insert, update, and delete data from your tables.He also covers creating a new database from scratch, as well as data types, transactions, subselects, views, and stored routines.
Next we say for each row that is being changed we want you to set the value of model_hash.
There is a not a single method that controls updates to the products table.
Its very likely that more than a handful of scripts can update the product table at any time.
Some errors you can receive when doing this include “ERROR 1442 (HY000): Cant update table ‘tbl’ in stored function/trigger because it is already used by statement which invoked this stored function/trigger” as a result of bad syntax such as this: My SQL will prevent this trigger from executing because it will detect an infinite loop.
Because after an update, triggering an update, would of course trigger an after update trigger…
Using this approach I was able to chop a 14 second query down to 1 second.
In fact the application in question wouldn’t even load on our test server prior to me optimizing the code (there were other factors in play, but this about half of the performance penalties).
It looks like the "Create Trigger" code written by Workbench doesn't match what SHOW CREATE TRIGGER generates, so the resynch will always show changes waiting to be sent to source. Verify that the change was loaded, and then synchronize again. Also, I just tried to insert two triggers on the one table with model. Synchronize and bring triggers from source to model. Nothing has changed in the editor, but now now changes are shown pending.
Suggested fix: Fix triggers display status so that when model and source agree, no differences are reported. After the steps you took, resynch your model and source, and the your model will show changes to the trigger still waiting to be sent to the source. Synchronize again, and triggers 2 and 3 show changes waiting, even though they've already been sent to db.
Using the NEW keyword we tell it what the new value is, too read an older value we would have said OLD.model_hash.
Lastly the CONV(), RIGHT(), and MD5() are simply used to create a unique numerical hash (credit goes to the authors of High Performance My SQL for giving me the hashing idea).
My SQL is by far the most popular database management system for small- to medium-sized web projects.