Category Archives: sql

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 – IS NOT NULL Table of content A NULL value indicates a missing or unknown value. It appears to be blank and does not contain any data. It is very important to understand that a NULL value is different than a zero value or a field that contains spaces. For checking null values we […]

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 […]