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  • A2-03-03.DDL-MySQL Data Types

    转载自:http://www.mysqltutorial.org/mysql-data-types.aspx

    MySQL Data Types

     

    Summaryin 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.

    MySQL Data Types

    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 TypesDescription
     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 TypesDescription
     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 TypesDescription
     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 TypesDescription
     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.

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  • 原文地址:https://www.cnblogs.com/zhuntidaoren/p/9523342.html
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