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Big data training and sharing for good programmers mysql data type , Introduction to data types • Data type setting • Column properties • Character set usage of data types • Select the appropriate data type 2, Introduction to data types
• Four main categories ：
value type
Character type
Time type
Binary type
• Data type ABC essential factor ：
Appropriate（ appropriate ）
Brief（ concise ）
Complete（ complete ）
• example 1： Column declaration
CREATE TABLE people ( id INT, first_name CHAR(30), last_name CHAR(30) );
• example 2： Negative and unknown values are not allowed
CREATE TABLE people ( id INT UNSIGNED NOT NULL, first_name CHAR(30),
last_name CHAR(30) );3, Numerical data type
• Considerations when using numeric data types ：
The range of values represented by a data type
The amount of space required for column values
Column precision and range （ Floating point number and fixed point number ）
• Classes of numeric data types ：
integer ： integer
Floating point number ： decimal
Fixed point number ： Exact value
BIT： Bit field value
4, String data type
• Represents a sequence of alphanumeric characters in a given character set
• Used to store text or binary data
• It is implemented in almost every programming language
• Support character set and collation
• It belongs to one of the following categories
text ： Real unstructured string data type
integer ： Structured string type
5, Binary string data type
• Byte sequence
8-bit grouping
• Store binary values , for example ：
Compiled computer programs and Applications
Image and sound files
• Class of character binary data type ：
Binary ： Fixed and variable length binary strings
BLOB： Variable length unstructured collection of binary data
6, Time data type
7, Column properties
The category of the column property ：
• numerical value ： For numeric data types （BIT except ）
• character string ： For non binary string data types
• routine ： For all data types
8, How to select data type
• Consider which data types and character sets can minimize storage and disk I/O.
• Use fixed length data type ：
If all stored string values have the same length
• Use variable length data types ：
If the stored string values are different
For multibyte character sets
• For frequently used characters , Use a multibyte character set that takes less space .
Use Basic Multilingual plane (Basic Multilingual Plane, BMP) Other than Unicode character set .
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