Copy to another table on mysql update - mysql

Question

I have a mysql table that whenever there is an add, modify/update, or delete, I want to take the row and add it to an "archive" table (before it is updated or deleted). This is for a historical archive (i.e. what happened). Is there a way to do this in the database layer "automatically"? Is there a better way...

Answer 1

You'll need a group of triggers that cover all operations (insert, update, delete).
Let's say you have a table
CREATE TABLE table1
(
table1_id int not null auto_increment primary key,
column1 varchar(32)
);
and you created the following history table for it
CREATE TABLE table1_history
(
history_id int not null auto_increment primary key,
dt datetime not null,
operation varchar(6) not null,
table1_id int not null,
column1 varchar(32) not null
);
Now your triggers might look something like
CREATE TRIGGER tg_ai_table1
AFTER INSERT ON table1
FOR EACH ROW
INSERT INTO table1_history (dt, operation, table1_id, column1)
VALUES(NOW(), 'insert', NEW.table1_id, NEW.column1);
CREATE TRIGGER tg_au_table1
AFTER UPDATE ON table1
FOR EACH ROW
INSERT INTO table1_history (dt, operation, table1_id, column1)
VALUES(NOW(), 'update', NEW.table1_id, NEW.column1);
CREATE TRIGGER tg_bd_table1
BEFORE DELETE ON table1
FOR EACH ROW
INSERT INTO table1_history (dt, operation, table1_id, column1)
VALUES(NOW(), 'delete', OLD.table1_id, OLD.column1);
If we issue the following DML statements against table1
INSERT INTO table1 (column1) VALUES ('value1'), ('value2');
UPDATE table1 SET column1 = 'value11' WHERE table1_id = 1;
DELETE FROM table1 WHERE table1_id = 2;
table1 will contain
| TABLE1_ID | COLUMN1 |
|-----------|---------|
| 1 | value11 |
table1_history will contain
| HISTORY_ID | DT | OPERATION | TABLE1_ID | COLUMN1 |
|------------|--------------------------------|-----------|-----------|---------|
| 1 | January, 04 2014 06:31:15+0000 | insert | 1 | value1 |
| 2 | January, 04 2014 06:31:15+0000 | insert | 2 | value2 |
| 3 | January, 04 2014 06:31:15+0000 | update | 1 | value11 |
| 4 | January, 04 2014 06:31:15+0000 | delete | 2 | value2 |
Here is SQLFiddle demo

Answer 2

Try to use Trigger
eg:
DROP TRIGGER auditlog
CREATE TRIGGER auditlog BEFORE UPDATE ON frequencies
FOR EACH ROW BEGIN
INSERT INTO frequencies_audit select * from frequencies where freqId = NEW.freqId;
END;