两个字段的总和

Question

I have a mysql table with 2 fields: numPears(int) and numApples(int) and i'd like to have a numFruit(int) that automatically get these 2 values and sum them. Is that possible?

Example

So that if a query

INSERT INTO strange_table (fruitID, numPears, numApples) VALUES (1, 1, 5);

And then query

SELECT numFruit FROM strange_table WHERE fruitID = 1;

It returns me 6.

Answer 1

If you are looking to create a static value every time a new row comes into the DB, use a trigger. See http://dev.mysql.com/doc/refman/5.0/en/create-trigger.html and in particular, triggers on insert and update.

-- You've clarified your question! I think stored procedures are more what you are looking for now!

http://dev.mysql.com/doc/refman/5.0/en/create-procedure.html

This lets you create a function inside MySQL called numFruit which returns the sum of the other two columns.