Question

I would like to find out if there’s a way one can update a record in mysql and
still be able to keep the previous(prior to update) data of the record and also keep an update history counter.

I should be able to use the last updated record as the true record.

Help appreciated.

Thanks.

Answer 1

I think you don’t need to update the record but instead Insert another record so your previous records will be untouched.

UPDATE 1

You need to create two tables for this. The first one is data which are the records and another is the table that holds it changes. example,

CREATE TABLE dataList
(
    ID INT NOT NULL,
    Name VARCHAR(30),
    -- other fields... ,
    CONSTRAINT dl_pk PRIMARY KEY ID)
);

CREATE TABLE versionList
(
    ID INT AUTO_INCREMENT,
    DataID INT,
    VersionID INT,
    DateChanged datetime,
    CONSTRAINT vl_pk PRIMARY KEY (ID),
    CONSTRAINT vl_fk FOREIGN KEY (DataID) 
        REFERENCES dataList(ID)
);

INSERT INTO dataList(ID, Name) VALUES (1,'hello');
INSERT INTO dataList(ID, Name) VALUES (2,'world');

INSERT INTO versionList(DataID, VersionID, DateChanged) VALUES (1,1,'2011-01-01');
INSERT INTO versionList(DataID, VersionID, DateChanged) VALUES (1,2,'2011-02-01');
INSERT INTO versionList(DataID, VersionID, DateChanged) VALUES (1,3,'2011-03-01');
INSERT INTO versionList(DataID, VersionID, DateChanged) VALUES (2,1,'2012-01-01');
INSERT INTO versionList(DataID, VersionID, DateChanged) VALUES (2,2,'2012-02-01');