A2-03-03.DDL-MySQL Data Types
转载自：http://www.mysqltutorial.org/mysql-data-types.aspx
MySQL Data Types
Summary: in this tutorial, you will learn about MySQL data types and how to use them effectively in designing database in MySQL.
A database table contains multiple columns with specific data types such as numeric or string. MySQL provides more data types other than just numeric or string. Each data type in MySQL can be determined by the following characteristics:
- The kind of values it represents.
- The space that takes up and whether the values is a fixed-length or variable length.
- The values of the data type can be indexed or not.
- How MySQL compares the values of a specific data type.
Download MySQL Data Types Overview
MySQL numeric data types
In MySQL, you can find all SQL standard numeric types including exact number data type and approximate numeric data types including integer, fixed-point and floating point. In addition, MySQL also hasBIT data type for storing bit values. Numeric types can be signed or unsigned except for the BIT type.
The following table shows the summary of numeric types in MySQL:
| Numeric Types | Description |
|---|---|
TINYINT |
A very small integer |
SMALLINT |
A small integer |
MEDIUMINT |
A medium-sized integer |
INT |
A standard integer |
BIGINT |
A large integer |
DECIMAL |
A fixed-point number |
FLOAT |
A single-precision floating point number |
DOUBLE |
A double-precision floating point number |
BIT |
A bit field |
MySQL Boolean data type
MySQL does not have the built-in BOOLEANor BOOL data type. To represent Boolean values, MySQL uses the smallest integer type which isTINYINT(1). In other words, BOOLEAN and BOOL are synonyms for TINYINT(1).
MySQL String data types
In MySQL, a string can hold anything from plain text to binary data such as images or files. Strings can be compared and searched based on pattern matching by using the LIKE operator, regular expression, and full-text search.
The following table shows the string data types in MySQL:
| String Types | Description |
|---|---|
CHAR |
A fixed-length nonbinary (character) string |
VARCHAR |
A variable-length non-binary string |
BINARY |
A fixed-length binary string |
VARBINARY |
A variable-length binary string |
TINYBLOB |
A very small BLOB (binary large object) |
BLOB |
A small BLOB |
MEDIUMBLOB |
A medium-sized BLOB |
LONGBLOB |
A large BLOB |
TINYTEXT |
A very small non-binary string |
TEXT |
A small non-binary string |
MEDIUMTEXT |
A medium-sized non-binary string |
LONGTEXT |
A large non-binary string |
ENUM |
An enumeration; each column value may be assigned one enumeration member |
SET |
A set; each column value may be assigned zero or more SET members |
MySQL date and time data types
MySQL provides types for date and time as well as the combination of date and time. In addition, MySQL supports timestamp data type for tracking the changes in a row of a table. If you just want to store the year without date and month, you can use the YEAR data type.
The following table illustrates the MySQL date and time data types:
| Date and Time Types | Description |
|---|---|
DATE |
A date value in CCYY-MM-DD format |
TIME |
A time value in hh:mm:ss format |
DATETIME |
A date and time value inCCYY-MM-DD hh:mm:ssformat |
TIMESTAMP |
A timestamp value in CCYY-MM-DD hh:mm:ss format |
YEAR |
A year value in CCYY or YY format |
MySQL spatial data types
MySQL supports many spatial data types that contain various kinds of geometrical and geographical values as shown in the following table:
| Spatial Data Types | Description |
|---|---|
GEOMETRY |
A spatial value of any type |
POINT |
A point (a pair of X-Y coordinates) |
LINESTRING |
A curve (one or more POINT values) |
POLYGON |
A polygon |
GEOMETRYCOLLECTION |
A collection of GEOMETRYvalues |
MULTILINESTRING |
A collection of LINESTRINGvalues |
MULTIPOINT |
A collection of POINTvalues |
MULTIPOLYGON |
A collection of POLYGONvalues |
JSON data type
MySQL supported a native JSON data type since version 5.7.8 that allows you to store and manage JSON documents more efficiently. The native JSON data type provides automatic validation of JSON documents and optimal storage format.
In this tutorial, you have learned various MySQL data types that help you determine which data type you should use for columns when you create tables.
