Syntax for nested queries in mysql - mysql

Question

I have 3 tables:
stocktake
supplier
accessories
I want to select total_inventories,accessory_id,supplier_id,conpany_name,phone_no
this 5 things in this three table
and the total_inventorieshave to <100
and I have to use Nested Query or either standard or correlated sub-query
that is what I have done
SELECT total_inventories,accessory_id,supplier_id,conpany_name,phone_no
FROM stocktake,supplier,accessories
WHERE stocktake.accessory_id=accessory.accessory_id,accessory.supplier_id=supplier.supplier_id,
accessory_id IN (SELECT accessory_id FROM stocktake WHERE total_inventories <100)
but it got an error
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'accessory.supplier_id=supplier.supplier_id,
accessory_id in (select accessory_i' at line 3
How can I fix it?

Answer 1

few things to mention in your code
you are using accessories table but using accessory.supplier_id. so you need to use correct the table name.
always use explicit join instead of implicit joins.
always use alias for the tables for more readability.
use exists instead of IN
FROM stocktake s
join accessories a
on s.accessory_id = a.accessory_id
join supplier su
on a.supplier_id = su.supplier_id
WHERE a.accessory_id IN (SELECT accessory_id FROM stocktake WHERE total_inventories < 100)
In your solution you can replace IN with exists as following
WHERE a.accessory_id exists
(
SELECT
accessory_id
FROM stocktake s
WHERE a.accessory_id = s.accessory_id
and total_inventories < 100
)

Answer 2

You cannot use comma in where operator try. You can also refer join operation in sql.
FROM stocktake,supplier,accessories
WHERE stocktake.accessory_id=accessory.accessory_id and accessory.supplier_id=supplier.supplier_id and
accessory_id IN (SELECT accessory_id FROM stocktake WHERE total_inventories <100)
The query can be optimized as:
FROM stocktake,supplier,accessories
WHERE stocktake.accessory_id=accessory.accessory_id and accessory.supplier_id=supplier.supplier_id and
stocktake.total_inventories <100
We would not need subquery, we can directly filter total_inventories values as we have already joined three tables.