SQL数据类型 


SQL数据类型

数据类型用于表示可以存储在数据库表中的数据的性质。例如,在表的特定列中,如果我们要存储字符串类型的数据,则必须声明此列的字符串数据类型。

每个数据库的数据类型主要分为三类。

  • 字符串数据类型
  • 数值数据类型
  • 日期和时间数据类型

MySQL,SQL Server和Oracle数据库中的数据类型

MySQL数据类型

MySQL数据库中使用的数据类型列表。这基于MySQL 8.0。

MySQL字符串数据类型

MySQL数值数据类型MySQL日期和时间数据类型SQL Server数据类型SQL Server字符串数据类型SQL Server数值数据类型SQL Server日期和时间数据类型SQL Server其他数据类型Oracle数据类型Oracle String数据类型Oracle数值数据类型Oracle日期和时间数据类型Oracle大对象数据类型(LOB类型)

CHAR(Size) It is used to specify a fixed length string that can contain numbers, letters, and special characters. Its size can be 0 to 255 characters. Default is 1.
VARCHAR(Size) It is used to specify a variable length string that can contain numbers, letters, and special characters. Its size can be from 0 to 65535 characters.
BINARY(Size) It is equal to CHAR() but stores binary byte strings. Its size parameter specifies the column length in the bytes. Default is 1.
VARBINARY(Size) It is equal to VARCHAR() but stores binary byte strings. Its size parameter specifies the maximum column length in bytes.
TEXT(Size) It holds a string that can contain a maximum length of 255 characters.
BIT(Size) It is used for a bit-value type. The number of bits per value is specified in size. Its size can be 1 to 64. The default value is 1.
INT(size) It is used for the integer value. Its signed range varies from -2147483648 to 2147483647 and unsigned range varies from 0 to 4294967295. The size parameter specifies the max display width that is 255.
INTEGER(size) It is equal to INT(size).
FLOAT(size, d) It is used to specify a floating point number. Its size parameter specifies the total number of digits. The number of digits after the decimal point is specified by d parameter.
FLOAT(p) It is used to specify a floating point number. MySQL used p parameter to determine whether to use FLOAT or DOUBLE. If p is between 0 to24, the data type becomes FLOAT (). If p is from 25 to 53, the data type becomes DOUBLE().
DOUBLE(size, d) It is a normal size floating point number. Its size parameter specifies the total number of digits. The number of digits after the decimal is specified by d parameter.
DECIMAL(size, d) It is used to specify a fixed point number. Its size parameter specifies the total number of digits. The number of digits after the decimal parameter is specified by d parameter. The maximum value for the size is 65, and the default value is 10. The maximum value for d is 30, and the default value is 0.
DEC(size, d) It is equal to DECIMAL(size, d).
BOOL It is used to specify Boolean values true and false. Zero is considered as false, and nonzero values are considered as true.
DATE It is used to specify date format YYYY-MM-DD. Its supported range is from ‘1000-01-01’ to ‘9999-12-31’.
DATETIME(fsp) It is used to specify date and time combination. Its format is YYYY-MM-DD hh:mm:ss. Its supported range is from ‘1000-01-01 00:00:00′ to 9999-12-31 23:59:59’.
TIMESTAMP(fsp) It is used to specify the timestamp. Its value is stored as the number of seconds since the Unix epoch(‘1970-01-01 00:00:00’ UTC). Its format is YYYY-MM-DD hh:mm:ss. Its supported range is from ‘1970-01-01 00:00:01’ UTC to ‘2038-01-09 03:14:07’ UTC.
TIME(fsp) It is used to specify the time format. Its format is hh:mm:ss. Its supported range is from ‘-838:59:59’ to ‘838:59:59’
YEAR It is used to specify a year in four-digit format. Values allowed in four digit format from 1901 to 2155, and 0000.
char(n) It is a fixed width character string data type. Its size can be up to 8000 characters.
varchar(n) It is a variable width character string data type. Its size can be up to 8000 characters.
varchar(max) It is a variable width character string data types. Its size can be up to 1,073,741,824 characters.
text It is a variable width character string data type. Its size can be up to 2GB of text data.
nchar It is a fixed width Unicode string data type. Its size can be up to 4000 characters.
nvarchar It is a variable width Unicode string data type. Its size can be up to 4000 characters.
ntext It is a variable width Unicode string data type. Its size can be up to 2GB of text data.
binary(n) It is a fixed width Binary string data type. Its size can be up to 8000 bytes.
varbinary It is a variable width Binary string data type. Its size can be up to 8000 bytes.
image It is also a variable width Binary string data type. Its size can be up to 2GB.
bit It is an integer that can be 0, 1 or null.
tinyint It allows whole numbers from 0 to 255.
Smallint It allows whole numbers between -32,768 and 32,767.
Int It allows whole numbers between -2,147,483,648 and 2,147,483,647.
bigint It allows whole numbers between -9,223,372,036,854,775,808 and 9,223,372,036,854,775,807.
float(n) It is used to specify floating precision number data from -1.79E+308 to 1.79E+308. The n parameter indicates whether the field should hold the 4 or 8 bytes. Default value of n is 53.
real It is a floating precision number data from -3.40E+38 to 3.40E+38.
money It is used to specify monetary data from -922,337,233,685,477.5808 to 922,337,203,685,477.5807.
datetime It is used to specify date and time combination. It supports range from January 1, 1753, to December 31, 9999 with an accuracy of 3.33 milliseconds.
datetime2 It is used to specify date and time combination. It supports range from January 1, 0001 to December 31, 9999 with an accuracy of 100 nanoseconds
date It is used to store date only. It supports range from January 1, 0001 to December 31, 9999
time It stores time only to an accuracy of 100 nanoseconds
timestamp It stores a unique number when a new row gets created or modified. The time stamp value is based upon an internal clock and does not correspond to real time. Each table may contain only one-time stamp variable.
Sql_variant It is used for various data types except for text, timestamp, and ntext. It stores up to 8000 bytes of data.
XML It stores XML formatted data. Maximum 2GB.
cursor It stores a reference to a cursor used for database operations.
table It stores result set for later processing.
uniqueidentifier It stores GUID (Globally unique identifier).
CHAR(size) It is used to store character data within the predefined length. It can be stored up to 2000 bytes.
NCHAR(size) It is used to store national character data within the predefined length. It can be stored up to 2000 bytes.
VARCHAR2(size) It is used to store variable string data within the predefined length. It can be stored up to 4000 byte.
VARCHAR(SIZE) It is the same as VARCHAR2(size). You can also use VARCHAR(size), but it is suggested to use VARCHAR2(size)
NVARCHAR2(size) It is used to store Unicode string data within the predefined length. We have to must specify the size of NVARCHAR2 data type. It can be stored up to 4000 bytes.
NUMBER(p, s) It contains precision p and scale s. The precision p can range from 1 to 38, and the scale s can range from -84 to 127.
FLOAT(p) It is a subtype of the NUMBER data type. The precision p can range from 1 to 126.
BINARY_FLOAT It is used for binary precision( 32-bit). It requires 5 bytes, including length byte.
BINARY_DOUBLE It is used for double binary precision (64-bit). It requires 9 bytes, including length byte.
DATE It is used to store a valid date-time format with a fixed length. Its range varies from January 1, 4712 BC to December 31, 9999 AD.
TIMESTAMP It is used to store the valid date in YYYY-MM-DD with time hh:mm:ss format.
BLOB It is used to specify unstructured binary data. Its range goes up to 232-1 bytes or 4 GB.
BFILE It is used to store binary data in an external file. Its range goes up to 232-1 bytes or 4 GB.
CLOB It is used for single-byte character data. Its range goes up to 232-1 bytes or 4 GB.
NCLOB It is used to specify single byte or fixed length multibyte national character set (NCHAR) data. Its range is up to 232-1 bytes or 4 GB.
RAW(size) It is used to specify variable length raw binary data. Its range is up to 2000 bytes per row. Its maximum size must be specified.
LONG RAW It is used to specify variable length raw binary data. Its range up to 231-1 bytes or 2 GB, per row.
TINYTEXT It holds a string with a maximum length of 255 characters.
MEDIUMTEXT It holds a string with a maximum length of 16,777,215.
LONGTEXT It holds a string with a maximum length of 4,294,967,295 characters.
ENUM(val1, val2, val3,…) It is used when a string object having only one value, chosen from a list of possible values. It contains 65535 values in an ENUM list. If you insert a value that is not in the list, a blank value will be inserted.
SET( val1,val2,val3,….) It is used to specify a string that can have 0 or more values, chosen from a list of possible values. You can list up to 64 values at one time in a SET list.
BLOB(size) It is used for BLOBs (Binary Large Objects). It can hold up to 65,535 bytes.

 

 

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