SQL
Course Process
Creating a basic table involves naming the table and defining its columns and each column’s data type.
The SQL CREATE TABLE statement is used to create a new table.
Syntax
The basic syntax of the CREATE TABLE statement is as follows −
CREATE TABLE table_name( column1 datatype, column2 datatype, column3 datatype, ..... columnN datatype, PRIMARY KEY( one or more columns ) );
CREATE TABLE is the keyword telling the database system what you want to do. In this case, you want to create a new table. The unique name or identifier for the table follows the CREATE TABLE statement.
Then in brackets comes the list defining each column in the table and what sort of data type it is. The syntax becomes clearer with the following example.
A copy of an existing table can be created using a combination of the CREATE TABLE statement and the SELECT statement. You can check the complete details at Create Table Using another Table.
Example
The following code block is an example, which creates a CUSTOMERS table with an ID as a primary key and NOT NULL are the constraints showing that these fields cannot be NULL while creating records in this table −
SQL> CREATE TABLE CUSTOMERS( ID INT NOT NULL, NAME VARCHAR (20) NOT NULL, AGE INT NOT NULL, ADDRESS CHAR (25) , SALARY DECIMAL (18, 2), PRIMARY KEY (ID) );
You can verify if your table has been created successfully by looking at the message displayed by the SQL server, otherwise you can use the DESC command as follows −
SQL> DESC CUSTOMERS; +---------+---------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +---------+---------------+------+-----+---------+-------+ | ID | int(11) | NO | PRI | | | | NAME | varchar(20) | NO | | | | | AGE | int(11) | NO | | | | | ADDRESS | char(25) | YES | | NULL | | | SALARY | decimal(18,2) | YES | | NULL | | +---------+---------------+------+-----+---------+-------+ 5 rows in set (0.00 sec)
