mySQL: get hash value for each row?

Question

Currently I\'m manually creating a string where I concatenate all the values in each row in my table. I\'m hashing this string for each row to get a hash value for the curre

Answer 1

^{Late to the party, but...}

You could add an updated field that gets updated whenever the row changes.
Then you only have to keep track of the timestamps, that show like this

updated: 2017-12-30 17:51:19 

This way not only you know if a row changed, but you also know when was the last update.
MySQL command:

ALTER TABLE mytable ADD `updated` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP
ON UPDATE CURRENT_TIMESTAMP;

The default precision is a second (that should be enough, if you only check from time to time if a row changed). But you could set a fraction of a second precision, like microseconds, if necessary

ALTER TABLE mytable ADD `updated` timestamp(6) NOT NULL
DEFAULT CURRENT_TIMESTAMP(6) ON UPDATE CURRENT_TIMESTAMP(6);

The timestamp will then show like

updated: 2017-12-30 17:51:19.123456 

Link to the documentation, this is for 8.0 but I've been using that on 5.7 successfully.