INSERT INTO table_name (column1, column2, column3,...)
VALUES (value1, value2, value3,...)
Now what to check:
If inserted value1 = null, change it to 0
How to do it via trigger? I googled for examples and I have never ever done a trigger, so it is rather confusing.
So far got only this:
CREATE TRIGGER testTrigger
AFTER INSERT, UPDATE, DELETE