SQL join two tables related by a single column primary key or foreign key pair using where clause

Description

In this page, we are going to discuss the usage of two or more tables in a joining with single column PRIMARY KEY and FOREIGN KEY.

Example:

Sample table: foods

Sample table: company

To get 'item_name' and 'item_unit' from 'foods' table and 'company_name' and 'company_city' form 'company' table after a joining with following conditions-

1. 'company_id' is primary key in 'company' table,

2. 'company_id' is foreign key in 'foods' table which is referencing to the, primary key of 'company' table,

3. 'company_id' of 'company' and 'foods' must be same,

4. 'company_city' of 'company' column must be 'London',

the following SQL statement can be used :

SQL Code:

SELECT foods.tem_name,foods.item_unit,
company.company_name, company.company_city
FROM foods ,company
WHERE  foods.company_id =company.company_id
AND company.company_city='London';

Output

ITEM_NAME                 ITEM_UNIT  COMPANY_NAME              COMPANY_CITY
------------------------- ---------- ------------------------- -------------
Cheez-It                  Pcs        Jack Hill Ltd             London
BN Biscuit                Pcs        Jack Hill Ltd             London
Mighty Munch              Pcs        Foodies.                  London
Pot Rice                  Pcs        Jack Hill Ltd             London

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