MySQL: How to INSERT VALUE INTO TABLE if a value in another table is NULL?

Question

I have:

INSERT INTO ItemTracking(`Item`, `Source`, `LeftSourceAt`)
SELECT `Item`, `Source`, now() FROM ItemAvailability WHERE Item = 'PA';

I want to execute the above query ONLY IF ItemBeingTracked in ItemAvailability is NULL.

Edit: If ItemAvailability.ItemBeingTracked == NULL Then do the above query.

and how do you identify a specific record of the table1 entity? do you have an id or something? — Ousmane D.
– Ousmane D., Commented Nov 20, 2017 at 21:24

Gordon Linoff · Accepted Answer · 2017-11-20 21:45:19Z

2

I think you would just add the condition to the WHERE:

INSERT INTO ItemTracking(Item, `Source`, LeftSourceAt)
    SELECT Item, `Source`, now()
    FROM ItemAvailability
    WHERE Item = 'PA' AND ItemBeingTracked IS NULL;

answered Nov 20, 2017 at 21:45

Gordon Linoff

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Comments

Ousmane D. · Accepted Answer · 2017-11-20 21:50:21Z

1

a bit rusty with SQL, but I believe this is one way to go about it.

INSERT INTO ItemTracking(`Item`, `Source`, `LeftSourceAt`)
SELECT `Item`, `Source`, now() 
FROM ItemAvailability 
WHERE Item = 'PA' AND ItemBeingTracked IS NULL;

edited Nov 20, 2017 at 21:50

answered Nov 20, 2017 at 21:40

Ousmane D.

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2 Comments

Grendizer Over a year ago

Instead of inserting only 'PA', it put all the rows in ItemAvailability

Ousmane D. Over a year ago

then your description is ambiguous, see Gordon's answer as he posted it first but I've updated mine to accommodate your comment.

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