Chapter 16. MySQL Data Types

MySQL offers a wide variety of data types to support the storage of different kinds of data. This chapter lists the full range of these data types and describes their functionality, syntax, and data storage requirements. For each data type, the syntax shown uses square brackets ([]) to indicate optional parts of the syntax. The following example shows how BIGINT is explained in this chapter: 

BIGINT[(display_size)]

This indicates that you can use BIGINT alone or with a display size value. The italics indicate that you do not enter display_size literally, but instead enter your own value. Thus, possible uses of BIGINT include: 

BIGINT
BIGINT(20)

Like the BIGINT type above, many MySQL data types support the specification of a display size. Unless otherwise specified, this value must be an integer between 1 and 255.

Table 16-1 lists the data types and categorizes them as numeric, string, date, or complex. You can find the full description of each data type later in this chapter.

Table 16-1. MySQL data types

Data type

Classification

BIGINT

Numeric

BLOB

String

CHAR

String

CHARACTER

String

CHARACTER VARYING

String

DATE

Date

DATETIME

Date

DEC

Numeric

DECIMAL

Numeric

DOUBLE

Numeric

DOUBLE PRECISION

Numeric

ENUM

Complex

FLOAT

Numeric

INT

Numeric

INTEGER

Numeric

LONGBLOB

String

LONGTEXT

String

MEDIUMBLOB

String

MEDIUMINT

Numeric

MEDIUMTEXT

String

NCHAR

String

NATIONAL CHAR

String

NATIONAL CHARACTER

String

NATIONAL VARCHAR

String

NUMERIC

Numeric

REAL

Numeric

SET

Complex

SMALLINT

Numeric

TEXT

String

TIME

Date

TIMESTAMP

Date

TINYBLOB

String

TINYINT

Numeric

TINYTEXT

String

VARCHAR

String

YEAR

Date

In the following cases, MySQL silently changes the column type you specify in your table creation to something else:

VARCHAR -> CHAR

When the specified VARCHAR column size is less than four characters, it is converted to CHAR.

CHAR -> VARCHAR

When a table has at least one column of a variable length, all CHAR columns greater than three characters in length are converted to VARCHAR.

TIMESTAMP display sizes

Display sizes for TIMESTAMP fields must be an even value between 2 and 14. A display size of 0 or greater than 14 will convert the field to a display size of 14. An odd-valued display size will be converted to the next highest even value.

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