Category Archives: sql

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 […]

SQL – UNION vs UNION ALL Table of content UNION and UNION ALL operators are just the SQL implementation of algebraic set operators. Both of them are used to retrieve the rows from multiple tables and return them as one single table. The difference between these two operators is that UNION only returns distinct rows […]

SQL – INTERSECT Table of content In mathematical set theory, the intersection of two sets is a collection of values that are common to both sets. In real-time scenarios, there will be a huge number of tables in a database that contains information. The user may find it challenging to gather common information from various […]