'subtract two column in mysql

I have 3 column in my database . column a column b column c. I want subtract column a and b then input result in column c. I use PHP and mysqli. if you have sample source I'm happy to introduce or advise how to write

mysql


Solution 1:[1]

Insert into table_name (column_c)
select column_a - column_b from table_name;

Solution 2:[2]

I know this is super old, but since it was the top result I got, here's a way forward for anyone else that's looking: check out generated columns.

A decent tutorial is here, and a quick google will get you plenty more on the topic.

For the question asked, the benefit of a generated column is that the math being done (subtraction, in this case) is done automatically by the database.

Sources

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Source: Stack Overflow

Solution Source
Solution 1 Priyanshu
Solution 2 jetsetter

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