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me@grafxflow

Written by me@grafxflow

08 Nov, 2012

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MySQL UPDATE a column value with add or subtract

If you have a numerical value in a MySQL database table, that you want to UPDATE by adding a value to it, or subtracting a value from it. This can be done with a single MySQL query.

So for an example, I have a database with a product which has a quantity of 10 in stock, somebody has just bought 5 so I need to subtract that value from the database quantity.

UPDATE products_table SET quantity = quantity - 5 WHERE product_id = 21

Later in the shop admin you receive new stock and so need to UPDATE the product quantity by adding 5 new items to its current quantity of 5.

UPDATE products_table SET quantity = quantity + 5 WHERE product_id = 21

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1 Response

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    15 Aug 2013
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me@grafxflow

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I am a Full-stack Developer who also started delving into the world of UX/UI Design a few years back. I blog and tweet to hopefully share a little bit of knowledge that can help others around the web. Thanks for stopping by!

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