Category Archives: sql

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 […]

SQL – Primary Key Table of content The SQL Primary Key The SQL Primary Key is a column (or combination of columns) that uniquely identifies each record in a database table. The Primary Key also speeds up data access and is used to establish a relationship between tables. Even though a table can only have […]

SQL – EXCEPT Table of content The SQL EXCEPT Operator The EXCEPT operator in SQL is used to retrieve all the unique records from the left operand (query), except the records that are present in the result set of the right operand (query). In other words, this operator compares the distinct values of the left […]