I wonder if there is any way to calculate the difference between values that are in the same column. For example: I have a table with 2 fields: date and balance. I need to add a new field containing the balance difference from one date to another.
Dia Saldo Variação
------------------------------
01/12 --- 10 ------- 0
02/12 --- 30 ------- 20
03/12 --- 70 ------- 40
04/12 --- 80 ------- 10
You can do this as follows:
SELECT
m.id,
m.data,
m.saldo,
IFNULL(saldo - (SELECT mt.saldo FROM movimento mt WHERE mt.id < m.id ORDER BY mt.id DESC LIMIT 0,1), 0) AS variacao
FROM movimento m
Take a look at sqlfiddle.com
I know two options, you bring this in a query as in Calculate between fields
SELECT ValorBoleto + TotalJuros AS Preco FROM fotoprodutos
or this SQL Formula
SELECT
name,
black,
yellow,
white,
qty_job
(SUM(black) + SUM(yellow) + SUM(white)*0.4) / qty_job AS total
FROM counter
GROUP BY name;
Another option is for you to do this via the programming language. When you save, you calculate the field before filling it. But in this case, we would need to know the programming language to help you better.