SQL – Foreign Key Table of content The SQL Foreign Key In SQL, a Foreign Key is a column in one table that matches a Primary Key in another table, allowing the two tables to be connected together. A foreign key also maintains referential integrity between two tables, making it impossible to drop the table […]

Left Join vs Right Join Table of content The main difference between the Left Join and Right Join can be observed in the way tables are joined. They are both types of Outer Joins; that is, they retain unmatched rows in one table and discard the unmatched rows of another. Left Join preserves the unmatched […]

SQL – Unique Key Table of content The SQL Unique Key The SQL Unique Key (or, Unique constraint) does not allow duplicate values in a column of a table. It prevents two records from having same values in a column. Unique Key is just an alternative to the Primary Key; as both Unique and Primary […]