Change Null with 0 - mysql

Question

I have tried to run a query I phpmyAdmin as follows
SELECT
orders_history.id,
orders_history.`items`,
orders_history.`transaction_id`,
orders_history.`quantity`,
estockClaims.`esquantity`,
IFNULL( esquantity, 0 ),
orders_history.`quantity` - estockClaims.`esquantity` AS myquantity
FROM orders_history
LEFT JOIN estockClaims
ON orders_history.transaction_id = estockClaims.transaction_id
AND orders_history.items = estockClaims.items
LIMIT 0 , 100
And it gives me this result:
----------------------------------------------------------------------
id items transaction_id quantity esquantity IFNULL(esquantity , 0 ) myquantity
1 FR 001 100 NULL 0 NULL
2 BR 002 10 NULL 0 NULL
3 WR 003 25 25 25 0
4 CR 004 50 3 3 47
How to solve this so that NULL is not NULL anyomre but change to 0. Thanks in advance.
Thanks

Answer 1

You already have it in the next column. What you need to do is to drop the original esquantity column and make an alias for the IFNULL... column, like this:
SELECT orders_history.id, orders_history.`items` , orders_history.`transaction_id` ,
orders_history.`quantity` , IFNULL( esquantity, 0 ) AS esquantity,
orders_history.`quantity` - estockClaims.`esquantity` AS myquantity
FROM orders_history
LEFT JOIN estockClaims ON orders_history.transaction_id = estockClaims.transaction_id
AND orders_history.items = estockClaims.items
LIMIT 0 , 100
The change I mentioned is in the line 2 above.
UPDATE
To get
orders_history.`quantity` - estockClaims.`esquantity` AS myquantity
to show expected results, you need to "unnullify" the esquantity field again so that the subtraction would work:
orders_history.`quantity` - IFNULL( estockClaims.`esquantity`, 0 ) AS myquantity
That would ensure you no longer get, for example:
100 - NULL
but this instead:
100 - 0
which will return a proper value.
You can also skip the whole subtraction thing if esquantity is NULL and simply use the value of quantity.

Answer 2

you can use IF to check the esquantity and myquantity columns:
IF(esquantity IS NULL, 0, esquantity)
and
IF(myquantityIS NULL, 0, myquantity)
or use IFNULL as DanFromGermany said

Answer 3

Reason is you are using it as select instead of when doing subtraction. Use it as below:
SELECT orders_history.id, orders_history.`items` , orders_history.`transaction_id` , orders_history.`quantity` , orders_history.`quantity` - IFNULL( esquantity, 0 ) AS myquantity
FROM orders_history
LEFT JOIN estockClaims ON orders_history.transaction_id = estockClaims.transaction_id
AND orders_history.items = estockClaims.items
LIMIT 0 , 100

Answer 4

select temp.id, items, transaction_id, quantity, ifNULL(esquantity, 0), ifNULL(myquantity, 0)
from (SELECT
orders_history.id,
orders_history.`items`,
orders_history.`transaction_id`,
orders_history.`quantity`,
estockClaims.`esquantity`
orders_history.`quantity` - estockClaims.`esquantity` AS myquantity
FROM orders_history
LEFT JOIN estockClaims
ON orders_history.transaction_id = estockClaims.transaction_id
AND orders_history.items = estockClaims.items
LIMIT 0 , 100) temp

Answer 5

You can also use COALESCE to replace the NULL value to 0
check this query.
SELECT orders_history.id, orders_history.`items` , orders_history.`transaction_id` ,
orders_history.`quantity` , COALESCE( esquantity, 0 ) AS esquantity,
orders_history.`quantity` - COALESCE(estockClaims.`esquantity`, 0) AS myquantity
FROM orders_history
LEFT JOIN estockClaims ON orders_history.transaction_id = estockClaims.transaction_id
AND orders_history.items = estockClaims.items
LIMIT 0 , 100