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.
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 :
SELECT foods.item_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';
Outputs of the said SQL statement shown here is taken by using Oracle Database 10g Express Edition.
Here is a new document which is a collection of questions with short and simple answers, useful for learning SQL as well as for interviews.