SQL FOREIGN KEY

A FOREIGN KEY in one table points to a PRIMARY KEY in another table.
The FOREIGN KEY constraint also prevents that invalid data form being inserted into the foreign key column, because it has to be one of the values contained in the table it points to.
The foreign key can be used to cross-reference tables

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SYNTAX :

SELECT foreign key("column_name")
FROM "table_name"

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There are two tables given below from which concept of foreign can be understood.

table 'customers' id name age city bill 1 Tom 34 Paris 5300 2 Jhony 51 London 400 3 Ram 64 Delhi 20000.7 4 Simon 23 Portland 32.65 table 'orders' O_Id OrderNo P_Id 1 95 3 2 78 3 3 56 2 4 62 1 Online Execute/Compile select foreign key(NAME) from customers ; Aptitude / Reasoning / Interview Physical education & sports