Use of MySQL triggers (memo)

Trigger creation syntax four elements:

1. Monitoring Location (table)

2. Monitoring Events (Insert/update/delete)

3. Trigger Time (After/before)

4. Trigger Event (Insert/update/delete)

Grammar:

Create TRIGGER Trigger Name

After/before insert/update/delete on table name

For each row

Begin

SQL statements;

End

Not difficult to understand, such as before insert on table name, is triggered before the insert operation.

Note the use of old and new, which represents the data for the original row, and new represents the data for the row.

Insert only new--insert operation, not difficult to understand, only the new data

Delete only old--the same reason, the deletion operation only the original data

Update has both new and old--data, respectively, after the update and before the update

Use of MySQL triggers (memo)