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CREATING A TABLE

As you know that a table is a collection of organised data in the form of rows and columns. It is also
known as a relation. The CREATE TABLE command is used to create a table in SQL. The syntax to

create a table is:
CREATE TABLE table_name

(
column_name1 data_type (size),

column_name2 data_type (size),
column_name3 data_type (size),

.....
.....

column_nameN data_type (size)
);

While creating a table in SQL, it is necessary to give a data type for each field/column.

Let us create a table named Students having StudentId, FirstName, LastName, and Marks fields in
the following way:
CREATE TABLE Students

(

StudentID INTEGER,
FirstName CHAR(30),

LastName CHAR(30),
Marks INT

);
In the preceding code, you have noticed that a value 30 is given with the CHAR data type within the
parentheses as its size. The meaning of 30 is that you can store a string value up to 30 characters in
the FirstName and LastName fields. Whether you store a single character or 30 characters, this field
will always occupy space for 30 characters regardless of the actual string length. If you store one

character, 29 blank spaces will be inserted with the character.

Applying Constraints in the Table

SQL constraints are used to define rules for table data. These rules control the data that can be
stored in a column. Constraints are used to restrict the types of data that can be entered into a table.

NULL Constraint

The NULL constraint allows a column to store the NULL value, which means that if the column
does not receive any value during insert or update operations, it will accept the values of the other

columns in insert operations without showing any error.

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Introduction to MySQL