MySQL INT Data Type

 MySQL INT Data Type

Summary: in this tutorial, you will learn about MySQL INT or integer data type and how to use it in your database table design. In addition, we will show you how to use the display width and ZEROFILL attributes of an integer column.

Introduction to MySQL INT type

In MySQL, INT stands for the integer that is a whole number. An integer can be written without a fractional component e.g., 1, 100, 4, -10, and it cannot be 1.2, 5/3, etc. An integer can be zero, positive, and negative.

MySQL supports all standard SQL integer types INTEGER or INT and SMALLINT. In addition, MySQL provides TINYINT MEDIUMINT, and BIGINT as extensions to the SQL standard.

MySQL INT the data type can be signed and unsigned. The following table illustrates the characteristics of each integer type including storage in bytes, minimum value, and maximum value.

Type	Storage	Minimum Value	Maximum Value
	(Bytes)	(Signed/Unsigned)	(Signed/Unsigned)
TINYINT	1	-128	127
		0	255
SMALLINT	2	-32768	32767
		0	65535
MEDIUMINT	3	-8388608	8388607
		0	16777215
INT	4	-2147483648	2147483647
		0	4294967295
BIGINT	8	-9223372036854775808	9223372036854775807
		0	18446744073709551615

MySQL INT data type examples

Let’s look at some examples of using integer data types.

A) Using MySQL INT for a column example

Because integer type represents exact numbers, you usually use it as the primary key of a table. In addition, the INT the column can have an AUTO_INCREMENT attribute.

When you insert a NULL value or 0 into the INT AUTO_INCREMENT column, the value of the column is set to the next sequence value. Notice that the sequence value starts with 1.

When you insert a value, which is not NULL or zero, into the AUTO_INCREMENT column, the column accepts the value. In addition, the sequence is reset to the next value of the inserted value.

First, create a new table named items with an integer column as the primary key:

CREATE TABLE items (
    item_id INT AUTO_INCREMENT PRIMARY KEY,
    item_text VARCHAR(255)
);

You can use either INT or INTEGER in the CREATE TABLE the statement above because they are interchangeable. Whenever you insert a new row into the items table, the value of the item_id the column is increased by 1.

Next, the following INSERT statement inserts three rows into the items table.

INSERT INTO 
    items(item_text)
VALUES
    ('laptop'), 
    ('mouse'),
    ('headphone');

Then, query data from the items table using the following SELECT statement:

SELECT * FROM items;

After that, insert a new row whose value of the item_id the column is specified explicitly.

INSERT INTO items(item_id,item_text)
VALUES(10,'Server');

Since the current value of the item_id the column is 10, the sequence is reset to 11. If you insert a new row, the AUTO_INCREMENT the column will use 11 as the next value.

INSERT INTO items(item_text)
VALUES('Router');

Finally, query the data of the items table again to see the result.

SELECT * FROM items;

Note that starting from MySQL 5.1, the AUTO_INCREMENT column accepts only positive values and does not allow negative values.

B) Using MySQL INT UNSIGNED example

First, create a table called classes that has the column total_member with the unsigned integer data type:

CREATE TABLE classes (
    class_id INT AUTO_INCREMENT,
    name VARCHAR(255) NOT NULL,
    total_member INT UNSIGNED,
    PRIMARY KEY (class_id)
);

Second, insert a new row into the classes table:

INSERT INTO classes(name, total_member)
VALUES('Weekend',100);

It worked as expected.

Third, attempt to insert a negative value into the total_member column:

INSERT INTO classes(name, total_member)
VALUES('Fly',-50);

MySQL issued the following error:

Error Code: 1264. Out of range value for column 'total_member' at row 1

MySQL INT with the display width attribute

MySQL provides an extension that allows you to specify the display width along with the INT datatype. The display width is wrapped inside parentheses following the INT keyword e.g., INT(5) specifies an INT with the display width of five digits.

It is important to note that the display width attribute does not control the value ranges that the column can store. The display width attribute is typically used by the applications to format the integer values. MySQL includes the display width attribute as the metadata of the returned result set.

MySQL INT with the ZEROFILL attribute

In addition to the display width attribute, MySQL provides a non-standard ZEROFILL attribute. In this case, MySQL replaces spaces with zero. Consider the following example.

First, create a table named zerofill_tests :

CREATE TABLE zerofill_tests(
    id INT AUTO_INCREMENT PRIMARY KEY,
    v1 INT(2) ZEROFILL,
    v2 INT(3) ZEROFILL,
    v3 INT(5) ZEROFILL
);

Second, insert a new row into the zerofill_tests table.

INSERT INTO zerofill_tests(v1,v2,v3)
VALUES(1,6,9);

Third, query data from the zerofill_tests table.

SELECT 
    v1, v2, v3
FROM
    zerofill_tests;

The v1 the column has a display width of 2 including ZEROFILL.Its value is 1 therefore, you see 01 it in the output. MySQL replaces the first space by 0.

The v2 column has a display with 3 including ZEROFILL. Its value is 6 therefore, you see 00 it as the leading zeros.

The v3 column has a display width of 5 with ZEROFILL, while its value is 9, therefore MySQL pads 0000 at the beginning of the number in the output.

Note that if you use ZEROFILL attribute for an integer column, MySQL will automatically add an UNSIGNED attribute to the column.

In this tutorial, you have learned how to use the MySQL INT the data type for designing database tables.