Question

Very quick question!

If a table FK has a null value is there any way that I can design my query so that it does not bother joining the table the foreign key is associated to. I am currently using Left Joins.

Is there another join I could use or can I do something like this in my query using PHP?

if (table foreign key == NULL) 
{   
do not join table that foreign key points to 
}

else 
{   
join table using foreign key value 
}

Thanks

Answer 1

Can you post your table and key names? we can then write the query – I think it needs to be an inner join to avoid the nulls.

select * from table1
inner join table2
on table1.pk = table2.fk
where {your conditions}

For your schema

select * from procedure
inner join dosage on dosage.dosage_id = procedure.dosage_id

Why not deal with your NULL with a CASE statement and push an empty string instead?

SELECT *, CASE dosage_id
WHEN (dosage_id IS NULL) THEN ''
END
from procedure
inner join dosage on dosage.dosage_id = procedure.dosage_id

(note: I’m not the best at CASE – 😉 hopefully that gets you close enough)