Question

I am really a beginner in mysql. In oracle we can use triggers , which can detect the insert elements and allows to fully break the insert command if something is wrong. I’ve found that mysql also supports triggers, but how can we use them for detecting insert parameters and stopping them to be inserted if they don’t satisfy rules.

e.g. INSERT INTO accounts (userId, balance) VALUES ('12','450'); // Valid
     INSERT INTO accounts (userId, balance) VALUES ('12','-574'); // Invalid

if(balance<0){
  Do not insert;
}
else{
   Insert;
}

NOTE: I’m dealing with concurrent transactions, so STRICTLY need triggers, i.e. lowest level error detection so that no one can hack.
Any help will be appreciated. Thanks,

Answer 1

Or use an BEFORE INSERT trigger

DELIMITER $$

CREATE TRIGGER au_a_each BEFORE INSERT ON accounts FOR EACH ROW
BEGIN
IF new.balance > 0 THEN
  BEGIN
    INSERT INTO b (id,balance) VALUES (new.id, new.balance);
  END 
END $$
DELIMITER ;

More info in the mysql documentation : http://dev.mysql.com/doc/refman/5.0/en/create-trigger.html

PS: Programming lesson number 1(One with capital “o”) – Befriend whatever programming/scripting language’s documentation