Avoid inserting duplicate column values

Question

I have a very simple table with 3 columns tag_id, label, timestamp and I need as lightweight as possible a query to insert only when there is a new value for the column label.

How would I write an sql query to do this? I can see some examples already on the site but they are all mixed up in more complex queries (some involving subqueries) that I can't understand.

There seems to be different ways of doing it and I need to find out the most lightweight one so that I can repeat it in a loop to insert multiple tags in one go without putting too much strain on the server.

label is just a char at the moment - should I set it as unique somewhere then? :) — Amy Neville
– Amy Neville, Commented Jun 11, 2013 at 10:53
oh wow, so I just set a unique constraint to the column? wow ok.. — Amy Neville
– Amy Neville, Commented Jun 11, 2013 at 11:00

Explosion Pills · Accepted Answer · 2013-06-11 11:05:21Z

3

You can use

ALTER TABLE `tableName` ADD UNIQUE KEY (label);

This will enforce a unique value for that column in the schema. You will get an error when you attempt to insert a duplicate value. If you want to simply ignore the error, you can use INSERT IGNORE INTO.

answered Jun 11, 2013 at 11:05

Explosion Pills

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Nono · Accepted Answer · 2013-06-11 11:12:48Z

-1

you can also use:

INSERT INTO table(`label`) VALUES ("new value") 
 ON DUPLICATE KEY UPDATE `label` = "new value";

answered Jun 11, 2013 at 11:12

Nono

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Ike Walker Over a year ago

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