I am making a shopping cart. Selected items are stored inside a database based on a search query.

How I can add the quantity for rows in case sku, type and color are the same values?

example:

```
sku  type   color  quantity
---------------------------
1    type1  blue   5
1    type1  blue   2
2    type1  blue   5
1    type1  green  5

```

my new rows should be:

```
sku  type   color  quantity
---------------------------
1    type1  blue   7
2    type1  blue   5
1    type1  green  5

```

Notice the first row quantity is now 7.

How can this be done? I tried `GROUP BY`, but didn't know how to make it dynamic to match all.