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SQL Tutorial >> SQL Create Table.


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SQL Tutorial will guide us that tables are the basic structure where data is stored in the database. Given that in most cases, there is no way for the database vendor to know ahead of time what your data storage needs are, chances are that you will need to create tables in the database yourself. Many database tools allow you to create tables without writing SQL, but given that tables are the container of all the data, it is important to include the CREATE TABLE syntax in this tutorial.

Before we dive into the SQL syntax for CREATE TABLE, it is a good idea to understand what goes into a table. Tables are divided into rows and columns. Each row represents one piece of data, and each column can be thought of as representing a component of that piece of data. So, for example, if we have a table for recording employees information, then the columns may include information such as First Name, Last Name, Address, City, Country, Date of Birth, Gender and so on. As a result, when we specify a table, we include the column headers and the data types for that particular column.

So what are data types? Typically, data comes in a variety of forms. It could be an integer (such as 1), a real number (such as 0.55), a string (such as 'John Austin'), a date/time expression (such as '2007-JAN-01 10:00:00'), or even in binary format. When we specify a table, we need to specify the data type associated with each column (i.e., we will specify that 'First Name' is of type char(50) - meaning it is a string with 50 characters). One thing to note is that different relational databases allow for different data types, so it is wise to consult with a database-specific reference first.

The SQL syntax for CREATE TABLE is:


CREATE TABLE "table_name"
("column 1" "data_type_for_column_1",
"column 2" "data_type_for_column_2",
... )

Real Example of Table:


CREATE TABLE employees
(First_Name char(50),
Last_Name char(50),
Gender char(1),
Address char(50),
City char(50),
Country char(25),
Birth_Date date)

Sometimes, we want to provide a default value for each column. A default value is used when you do not specify a column's value when inserting data into the table. To specify a default value, add "Default [value]" after the data type declaration. In the above example, if we want to default column "Address" to "Not Available" and City to "New York", we would type in

CREATE TABLE employees
(First_Name char(50),
Last_Name char(50),
Gender char(1) ,
Address char(50) default 'Not Available',
City char(50) default 'New York',
Country char(25),
Birth_Date date)

You can also limit the type of information of a table or a column can hold. This is done through the Constraints keyword, we will discus constraints in SQL Tutorial section of SQL Constraints.

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