Question

I have a table that I keep track of fees for a specific item. These fees can change over time so I have two columns (startDate, endDate) with the current set of fees always having an endDate in the far future. I already have a trigger that I use to do some calculations on the new row being entered but what I also want to have happen is if I enter an item that already has an entry I want to set the previous entry’s endDate to the day before the new entry’s startDate and the new endDate to a predetermined far-away date. Here is the code for what I tried first:

CREATE
DEFINER=`root`@`%`
TRIGGER `im`.`splitBeforeIns`
BEFORE INSERT ON `im`.`split`
FOR EACH ROW
BEGIN
    SET NEW.tcPercent = (NEW.tcOfficeFee / NEW.globalFee) * 100 , NEW.proPercent = 100 - NEW.tcPercent, NEW.endDate = 20501231;
    UPDATE im.split set endDate = ADDDATE(NEW.startDate, -1) where procKey = NEW.procKey AND endDate = 20501231;
END$$

The error I get is:

ERROR 1442: Can't update table 'split' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.

Answer 1

The answer to this might be unwelcome, but it is: You can’t do that.

A Trigger can’t update another row of the same table as the row, the trigger was called from.

The typical way to do that, is to create a stored procedure, that inserts into/Updates the target table, then updates the other row(s), all in a transaction.