When a MySQL operator is executed, the output of the operator is stored in a table. The table name usually has the same name as the operator. For example, if we execute an IN operator on two tables, it will create a table called “IN” with two columns: first column stores which rows from first table match the rows from second table and second column stores which rows from second table match first table.
In addition to storing output, these tables also store triggers. A trigger is a stored procedure that executes automatically when data changes on a given MySQL table. In order to work properly, triggers need inputs from SQL operators such as INSERT or UPDATE.
A trigger can be created on specific columns of a given MySQL Table by specifying those columns in the CREATE TRIGGER