As when you update one of the values in the table to update the other, so that the updated value was a number from -10 from the first?

Question

As when you update one of the values in the table to update the other, so that the updated value was a number from -10 from the first?

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Don't know how to formulate correctly in MySql, not good.

This:
Table test_table in her columns id_product, quantity and quantity_stock - everywhere Integer

Need:
So when you update the column quantitycolumn quantity_stock took a value = new value of quantity - 10

Here at all that I had, and apparently, I don't understand:

CREATE TRIGGER update_test AFTER UPDATE ON test_table FOR EACH ROW BEGIN IF NEW.quantity <=> OLD.quantity THEN UPDATE test_table SET quantity_stock = NEW.quantity - 10; END IF; END;

asked May 10, 2019 by IvanIlyasov | 38 views

2 Answers

jackkum · Answer 1 · 2019-05-14T13:26:17+0000

Change the trigger to BEFORE UPDATE and just set the new value before the change.

CREATE TRIGGER update_test BEFORE UPDATE ON test_table FOR EACH ROW BEGIN IF NEW.quantity <> OLD.quantity THEN SET NEW.quantity_stock = NEW.quantity - 10; END IF; END;

Rsa97 · Answer 2 · 2019-05-14T13:26:17+0000

And what hinders to make such changes directly in the query?

UPDATE `test_table` SET `quantity` = :newQuantity, `quantity_stock` = :newQuantity-10 WHERE `id_product` = :productId

As when you update one of the values in the table to update the other, so that the updated value was a number from -10 from the first?

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