Author Archives: user

SQL – IS NULL Table of content Let”s assume a table with NULL values in some of its fields. These fields indicate that no values are present in them. SQL allows users to create new records or modify existing ones without specifying a value for a field. If no value is provided, the field is […]

SQL – UNION Operator Table of content The SQL UNION Operator The SQL UNION operator is used to combine data from multiple tables by eliminating duplicate rows (if any). To use the UNION operator on multiple tables, all these tables must be union compatible. And they are said to be union compatible if and only […]

SQL – NOT NULL Constraint Table of content In a table, columns can typically accept NULL values by default. However, if you want to ensure that a particular column does not contain NULL values, you need to add the NOT NULL constraint/condition on that column. The SQL NOT NULL Constraint The NOT NULL constraint in […]