Merge Rows AND/OR Columns into one field in a GROUP BY - php

Question

My SQL table looks like
+-----+------------+--------------+--------------+-----------+------------+-----------+
| rid | ship_to_id | product_code | product_name | first_row | second_row | third_row |
+-----+------------+--------------+--------------+-----------+------------+-----------+
| 1 | 555 | A | Crystal | 1 | 2 | 3 |
| 1 | 555 | A | Crystal | 4 | 5 | 6 |
| 2 | 333 | B | Diamond | first | second | third |
| 2 | 333 | A | Crystal | ROW 1 | ROW 2 | ROW 3 |
| 2 | 333 | A | Crystal | ROW 4 | ROW 5 | ROW 6 |
+-----+------------+--------------+--------------+-----------+------------+-----------+
And I am trying to get following results
+-----+------------+--------------+-------------------------------------+
| rid | ship_to_id | product_name | data |
+-----+------------+--------------+-------------------------------------+
| 1 | 555 | Crystal | 1 2 3 4 5 6 |
| 2 | 333 | Diamond | first second third |
| 2 | 333 | Crystal | ROW 1 ROW 2 ROW 3 ROW 4 ROW 5 ROW 6 |
+-----+------------+--------------+-------------------------------------+
Can someone please tell me what is wrong with my code. Thanks
$query = mysql_query("SELECT * FROM mytable group by rid, ship_to_id, product_code, product_name");
while($row = mysql_fetch_array($query)) {
echo "$row[rid] $row[ship_to_id] $row[product_code] $row[product_name] $row[first_row] $row[second_row] $row[third_row] <br>";
}

Answer 1

You're forgetting product_code sometimes, I guess.
This probably is bad database design. You should learn about Database normalization and related techniques.
Third, SQL normally produces the same number of columns for every result record, so the best result you could have has rows like 1, 555, "A", "Crystal", "1 4 2 5 3 6" (notice these are 5 values). But I cannot think of a concatenation method that would produce the numbers in the 1 2 3 4 5 6 order. Depending on the better form of your database-schema-to-be, this might be something easier done in PHP than SQL.
If you're still up to concatenating all values into a single cell (as in the newly formatted example output), the you should try something along these lines:
SELECT
rid, ship_to_id, product_code, product_name,
GROUP_CONCAT(CONCAT(first_row,'#',second_row,'#',third_row) SEPARATOR '~') AS data
FROM tablename
GROUP BY rid, ship_to_id, product_code, product_name;
Notice that the values of first_row etc. are separated by a '#' and the values from distinct records by a '~' sign. You can find more options in the documentation of MySQL's GROUP_CONCAT().

Answer 2

you can try something like
select rid,ship_to_id,product_name,
GROUP_CONCAT(CONCAT(first_row,' ',second_row,' ',third_row) as new_val
from mytable
group by rid,ship_to_id,product_name;

Answer 3

As you group by the first 4 columns and use no aggregation function on the remaining ones, data will be lost when multiple record have the same values in the columns grouped by.
So basically the result will be like the following:
+-----+------------+--------------+------------------------------------+
| rid | ship_to_id | product_name | first_row | second_row | thrid_row |
+-----+------------+--------------+------------------------------------+
| 1 | 555 | Crystal | 1 | 2 | 3 |
| 2 | 333 | Diamond | first | second | third |
| 2 | 333 | Crystal | ROW 1 | ROW 2 | ROW 3 |
+-----+------------+--------------+------------------------------------+
That's what group by means. To keep the data of the fields containing varying data, you must use an aggregation function on them, like GROUP_CONCAT. Example:
SELECT rid, ship_to_id, product_code, product_name, GROUP_CONCAT(first_row), GROUP_CONCAT(second_row), GROUP_CONCAT(third_row)
FROM mytable
GROUP BY rid, ship_to_id, product_code, product_name
This will concatenate the values of the corresponding record like this:
+-----+------------+--------------+------------------------------------------+
| rid | ship_to_id | product_name | first_row | second_row | thrid_row |
+-----+------------+--------------+------------------------------------------+
| 1 | 555 | Crystal | 1 4 | 2 5 | 3 6 |
| 2 | 333 | Diamond | first | second | third |
| 2 | 333 | Crystal | ROW 1 ROW 4 | ROW 2 ROW 5 | ROW 3 ROW 6 |
+-----+------------+--------------+------------------------------------------+
However, your approach with GROUP BY is probably not be the best for this case. It would worth to think about to just order by the rid, ship_to_id, product_code, product_name columns, and then iterate through them in PHP with the given order and merge the corresponding rows there.
You may also have to reconsider you database design, as a query like this smells about a bad concept :)