How does the before update trigger work in MySQL?
The following statement creates a BEFORE UPDATE trigger on the sales table. The trigger is automatically fired before an update event occurs for each row in the sales table. If you update the value in the quantity column to a new value that is 3 times greater than the current value, the trigger raises an error and stops the update.
When to change default delimiter in MySQL before update trigger?
Third, specify the name of the table to which the trigger belongs after the ON keyword. Finally, specify the trigger body which contains one or more statements. If you have more than one statement in the trigger_body, you need to use the BEGIN END block. In addition, you need to change the default delimiter as follows:
What happens if you forgot to add the set clause?
You forgot to add the SET clause. This way it doesn’t actually change the value. TRIGGER IS EVIL. Thanks for contributing an answer to Stack Overflow! Please be sure to answer the question. Provide details and share your research! But avoid … Asking for help, clarification, or responding to other answers.
Which is an example of a before update trigger?
Let’s look at an example of using a BEFORE UPDATE trigger. The following statement creates a BEFORE UPDATE trigger on the sales table. The trigger is automatically fired before an update event occurs for each row in the sales table.
Can a trigger be applied on a specific column in SQL?
You can’t trigger on a particular column update in SQL. It is applied on a row. You can put your condition for columm in your trigger with an IF statement, as below: DELIMITER // CREATE TRIGGER myTrigger AFTER UPDATE ON myTable FOR EACH ROW BEGIN IF !
Can a after insert trigger update the same table?
An AFTER INSERT trigger cannot modify the same table, neither by issuing an UPDATE nor by something like this: ERROR 1442 (HY000): Can’t update table ‘tbl_test’ in stored function/trigger because it is already used by statement which invoked this stored function/trigger.