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What is a NULL entity in SQL?
Null is an entity in SQL that is used to specify that a value does not exist. It is a reserved keyword
in SQL.
Most SQL languages use the expression IS NULL in the where clause for matching
records with NULL values, instead of comparing with NULL using an equality operator.
See code example below:
SELECT FIRSTNAME FROM T_STUDENTS WHERE LASTNAME IS NULL;
Following functions handle Null values:
Coalesce - This function returns the first non NULL value from a list of values.
NullIf - This function accepts 2 paramaters. If both parameters are equal, NULL is returned, else
the first paramater's value is returned.
SQL Queries
SQL
Create Table
DDL, Create, Alter, Drop commands
DML, Select, Insert, Update, Delete
Create Database
ACID Rules
Dual Table
NULL
Join, Inner, Outer, Left, Right, Full, Cartesian, Natural, Equi
Table, View and a Synonym?
Execute
Function
Stored Procedure
Syntax Stored Proc
Stored Procedure Vs. Function
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