SQL tutorials 17: SQL Primary Key constraint, Drop primary Key смотреть онлайн

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SQL tutorial on Primary key / SQL Primary key,
In this tutorial you will learn about
simple primary key, composute primary key, how to drop primary key. defining primary key using create table and alter table along with many other things.

Tool used in this tutorial is SQL Developer.
This tutorial series is part of SQL expert exam certification training. if you are preparing for SQL certification you can use my tutorials. This SQL Tutorial is a part of free training.

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This is Manish from RebellionRider.com

So Primary Key
There are two types of Primary keys
First is Simple primary Key: Primary key which Involves only one column and
Second is Composite Primary Key: Primary Key which involves more than one column.
We will start with Simple primary key.
You can create Primary key either with Create Table statement of by using Alter table Statement.
Let's define simple primary key using create table statements.
With create table statement we can either define primary key at column level or at table level.
We will start with defining Primary key at column level using create table statement.
You just have to put keyword Primary key after data type and size of column while defining a column of a table. Here oracle server will create a primary key on product id with default constraint name which will be slightly difficult to understand. You can give your own name to your constraint which is also a good practice.