Latest web development tutorials

×

×

×

×

SQL Tutorial

SQL Tutorial SQL Introduction SQL grammar SQL SELECT SQL SELECT DISTINCT SQL WHERE SQL AND & OR SQL ORDER BY SQL INSERT INTO SQL UPDATE SQL DELETE

SQL Advanced Tutorial

SQL SELECT TOP SQL LIKE SQL Wildcards SQL IN SQL BETWEEN SQL Alias SQL JOIN SQL INNER JOIN SQL LEFT JOIN SQL RIGHT JOIN SQL FULL JOIN SQL UNION SQL SELECT INTO SQL INSERT INTO SELECT SQL CREATE DB SQL CREATE TABLE SQL constraint SQL NOT NULL SQL UNIQUE SQL PRIMARY KEY SQL FOREIGN KEY SQL CHECK SQL DEFAULT SQL CREATE INDEX SQL DROP SQL ALTER SQL Auto Increment SQL view SQL date SQL NULL value SQL NULL function SQL Generic data types SQL DB type of data

SQL function

SQL function SQL AVG() SQL COUNT() SQL FIRST() SQL LAST() SQL MAX() SQL MIN() SQL SUM() SQL GROUP BY SQL HAVING SQL UCASE() SQL LCASE() SQL MID() SQL LEN() SQL ROUND() SQL NOW() SQL FORMAT() SQL Quick Reference SQL Host SQL to sum up

SQL NOT NULL constraint

Previous: SQL constraint

Next: SQL UNIQUE constraint

In case of default, a table column accepts NULL values.

SQL NOT NULL constraint

NOT NULL constraints forced the column does not accept NULL values.

NOT NULL constraint mandatory field always contains a value. This means that if you do not add value to a field, you can not insert a new record or update the record.

The following SQL mandatory "P_Id" column and the "LastName" column does not accept NULL values:

CREATE TABLE Persons
(
P_Id int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255)
)

Previous: SQL constraint

Next: SQL UNIQUE constraint