Create Oracle Table
نشر بواسطة : Obay Salah , November 26, 2024
In Oracle, CREATE TABLE statement is used to create a new table in the database.
To create a table, you have to name that table and define its columns and datatype for each column.
Syntax:
CREATE TABLE table_name ( column1 datatype [ NULL | NOT NULL ], column2 datatype [ NULL | NOT NULL ], ... column_n datatype [ NULL | NOT NULL ] );
Parameters used in syntax
- table_name: It specifies the name of the table which you want to create.
- column1, column2, ... column n: It specifies the columns which you want to add in the table. Every column must have a datatype. Every column should either be defined as "NULL" or "NOT NULL". In the case, the value is left blank; it is treated as "NULL" as default.
Oracle CREATE TABLE Example
Here we are creating a table named customers. This table doesn't have any primary key.
CREATE TABLE customers ( customer_id number(10) NOT NULL, customer_name varchar2(50) NOT NULL, city varchar2(50) );
This table contains three columns
- customer_id: It is the first column created as a number datatype (maximum 10 digits in length) and cannot contain null values.
- customer_name: it is the second column created as a varchar2 datatype (50 maximum characters in length) and cannot contain null values.
- city: This is the third column created as a varchar2 datatype. It can contain null values.
Oracle CREATE TABLE Example with primary key
CREATE TABLE customers ( customer_id number(10) NOT NULL, customer_name varchar2(50) NOT NULL, city varchar2(50), CONSTRAINT customers_pk PRIMARY KEY (customer_id) );
What is Primary key
A primary key is a single field or combination of fields that contains a unique record. It must be filled. None of the field of primary key can contain a null value. A table can have only one primary key.
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