Sum of table fields with PHP and Codeigniter

Question

I need to add some fields from a table. I have the transaction id and need to add all fields amount with id 224, all with 222.

Answer 1

You can do this using the function SUM and grouping the records by the field you want with GROUP BY. Example:

SELECT `customer_id`,  SUM(`amount`) AS `amount` 
FROM `tb_customer_credit` 
GROUP BY `customer_id`;

Sqlfiddle

So you have the sum of all the records. If you need the sum of only one record, you can do it the way @Bernardokowacic did, using the WHERE.

Answer 2

You can do this using only a select in the database, making your life easier. In your case the select will be as follows:

select sum(amount) as 'amount' from `tb_customer_credit` where customer_id = 224

Referring to the above line of code, you will only need to replace the value 224 by the name of the variable that will be used by your application to send the ID.

You could also get the most value, among other things using select only, thus decreasing the amount of things in php and decreasing your site’s response time.