Duplicating rows in one select MySql query - mysql

Question

At first I would like greet all Users and apologize for my english :).
I'm new user on this forum.
I have a question about MySQL queries.
I have table Items with let say 2 columns for example itemsID and ItemsQty.
itemsID ItemsQty
11 2
12 3
13 3
15 5
16 1
I need select itemsID but duplicated as many times as indicated in column ItemsQty.
itemsID ItemsQty
11 2
11 2
12 3
12 3
12 3
13 3
13 3
13 3
15 5
15 5
15 5
15 5
15 5
16 1
I tried that query:
SELECT items.itemsID, items.itemsQty
FROM base.items
LEFT OUTER JOIN
(
SELECT items.itemsQty AS Qty FROM base.items
) AS Numbers ON items.itemsQty <=Numbers.Qty
ORDER BY items.itemsID;
but it doesn't work correctly.
Thanks in advance for help.

Answer 1

SQL answer - Option 1
You need another table called numbers with the numbers 1 up to the maximum for ItemsQuantity
Table: NUMBERS
1
2
3
4
5
......
max number for ItemsQuantity
Then the following SELECT statement will work
SELECT ItemsID, ItemsQty
FROM originaltable
JOIN numbers
ON originaltable.ItemsQty >= numbers.number
ORDER BY ItemsID, number
See this fiddle -> you should always set-up a fiddle like this when you can - it makes everyone's life easier!!!
code answer - option 2
MySQL probably won't do what you want 'cleanly' without a second table (although some clever person might know how)
What is wrong with doing it with script?
Just run a SELECT itemsID, ItemsQty FROM table
Then when looping through the result just do (pseudo code as no language specified)
newArray = array(); // new array
While Rows Returned from database{ //loop all rows returned
loop number of times in column 'ItemsQty'{
newArray -> add 'ItemsID'
}
}//end of while loop
This will give you a new array
0 => 11
1 => 11
2 => 12
3 => 12
4 => 12
5 => 13
etc.

Answer 2

Select DISTINCT items.itemsID, items.itemsQty From base.items left outer join (select items.itemsQty as Qty from base.items) As Numbers On items.itemsQty <=Numbers.Qty
order by items.itemsID;
Use DISTINCT to remove duplicates. Read more here - http://dev.mysql.com/doc/refman/5.0/en/select.html

Answer 3

It seems like I understood what you asked differently than everyone else so I hope I answer you question. What I would basically do is -
create a new table for those changes.
Create a mysql procedure which given a line in the original table add new lines to the new table - http://dev.mysql.com/doc/refman/5.6/en/loop.html
Run this procedure for each line in the original table.

Answer 4

try this to get distinct values from both columns
SELECT DISTINCT itemsID FROM items
UNION
SELECT DISTINCT itemsQty FROM items