SQL for retrieving data from all the rows for a particular id in the list and then call a function?

Question

Any performance issues in the code below:

Goal: I want retrieve data from all the rows for a particular id in the list and then call a function

a = list of 2000 ids:

for (int i = 0; i < a.size; i++) {
    // Execute query "SELECT * FROM SOME_TABLE WHERE ID = I";
    // Use the data and call a function
}

Any other solution? Is it possible to have just one query with group by id and whenever group changes call a function.

Thanks

Answer 1

You could use an ORDER BY clause to order the results by id and then as you said, simply keep track of the current id and call the function every time the next id doesn't match the current (and if you get to the end of the result set).

Answer 2

If you can express the function / grouping in SQL, that will be probably be faster. But that depends on what the function does.

It could look like

  select id, max(amount), sum(amount) from some_table group by id