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Building an inventory system. I have lots of products and each product has three different variables. So for stock totals I want to group by the two columns (product & size) and sum quantity to get stock total.

product Size Quantity
Widget one 2 275
Widget one 2 100
Widget two 3 150
Widget two 2 150

What I want for output:

product Size Quantity
Widget one 2 375
Widget two 3 150
Widget two 2 150

I figured out how to group by one column and sum using the code below:

$query = "SELECT product, SUM(Quantity) FROM inventory GROUP BY product";  
$result = mysql_query($query) or die(mysql_error());
// Print out result
while($row = mysql_fetch_array($result)){
    echo "Total ". $row['product']. " = ". $row['SUM(Quantity)'];
    echo "<br />";

I am just stuck on grouping by both columns. Is it possible? or should I just create three different products for the of the three sizes and eliminate that column? Thanks.



Based on your example table, it appears you want to be grouping on product rather than id. You merely need to add the Size column to both the SELECT list and the GROUP BY

$query = "SELECT 
            SUM(Quantity) AS TotalQuantity 
          FROM inventory
          GROUP BY product, Size";

Note that I have added a column alias TotalQuantity, which will allow you to more easily retrieve the column from the fetched row via the more sensible $row['TotalQuantity'], rather than $row['SUM(Quantity)']

Sunday, September 25, 2022

I would say just build it yourself. You can set it up like this:

$query = "INSERT INTO x (a,b,c) VALUES ";
foreach ($arr as $item) {
  $query .= "('".$item[0]."','".$item[1]."','".$item[2]."'),";
$query = rtrim($query,",");//remove the extra comma
//execute query

Don't forget to escape quotes if it's necessary.

Also, be careful that there's not too much data being sent at once. You may have to execute it in chunks instead of all at once.

Saturday, November 5, 2022

The function you're looking for is find_in_set:

 select * from ... where find_in_set($word, pets)

for multi-word queries you'll need to test each word and AND (or OR) the tests:

  where find_in_set($word1, pets) AND find_in_set($word2, pets) etc 
Wednesday, August 17, 2022

Please try:

    SUM(ItemCount) ItemCount,
    SUM(Amount) Amount
GROUP BY Code, Type
Monday, December 26, 2022

Your query is fine. The reason you are getting 2000 rows is because you are getting one row for every unique pair of values user_id, item_id.

If you want to see the interaction types going into each row then use:

select user_id, item_id, max(interaction_type) as max_type,
       group_concat(distinct interaction_type) as interaction_types,
       count(*) as cnt
from mytable
group by user_id, item_id;

It occurs to me that you want all rows with the maximum interaction type. If so, calculate the maximum and then find all rows that match that value:

select t.*
from mytable t cross join
     (select max(interaction_type) as maxit from mytable) x
     on x.maxit = t.interaction_type;

No group by is needed for this query.

Tuesday, August 2, 2022
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