Question

I have a table that stores data that has been entered regarding the amount of waste put in a bin. So my table looks like this:

Material  |  Weight
===================
Paper     |  10
Plastic   |  5
Paper     |  7

As you can see, I’m going to have duplicate data in the table. At the moment I have multiple instances of different materials, and they all have different weight values attached to them.

Is it possible in PHP to get these duplicate entries, combine them in to one entry, and then display them? So the code would take the 10Kg of Paper and add it to the other instance of paper in the table (7Kg) and then output the value?

I have tried the GROUP BY in MySQL, but all that will do is combine all of the entries and give me the value of the top record, which isn’t right.

Thanks!

Answer 1

Use MySql, with a SUM column. This will sum up all values for that column, for each grouping. This is assuming the weight column is just a number (10 instead of 10kg).

SELECT 
    `material`, 
    SUM(`weight`) AS `weight` 
FROM `material_weights` 
GROUP BY `material`

If the weight column isn’t just a number (10kg instead of 10), then there will be issues.

If all weights are in KG, then you should just remove the ‘kg’ value from each weight, and convert the weight column from text into a numeric column.

If there are different kinds of weights (KG, LB, G, etc), then the best way would be to have an extra field in the table, with the weight converted into KG.