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📜  SQL-数据类型

📅  最后修改于: 2020-12-29 04:30:32             🧑  作者: Mango

SQL数据类型是一个属性，用于指定任何对象的数据类型。在SQL中，每个列，变量和表达式都有一个相关的数据类型。您可以在创建表时使用这些数据类型。您可以根据需要为表列选择数据类型。

SQL Server提供六类数据类型供您使用，以下列出-

确切的数值数据类型

DATA TYPE FROM TO
bigint -9,223,372,036,854,775,808 9,223,372,036,854,775,807
int -2,147,483,648 2,147,483,647
smallint -32,768 32,767
tinyint 0 255
bit 0 1
decimal -10^38 +1 10^38 -1
numeric -10^38 +1 10^38 -1
money -922,337,203,685,477.5808 +922,337,203,685,477.5807
smallmoney -214,748.3648 +214,748.3647

近似数值数据类型

DATA TYPE FROM TO
float -1.79E + 308 1.79E + 308
real -3.40E + 38 3.40E + 38

日期和时间数据类型

DATA TYPE FROM TO
datetime Jan 1, 1753 Dec 31, 9999
smalldatetime Jan 1, 1900 Jun 6, 2079
date Stores a date like June 30, 1991
time Stores a time of day like 12:30 P.M.

注意-这里的datetime精度为3.33毫秒，而smalldatetime的精度为1分钟。

字符的数据类型

Sr.No. DATA TYPE & Description
1

char

Maximum length of 8,000 characters.( Fixed length non-Unicode characters)
2

varchar

Maximum of 8,000 characters.(Variable-length non-Unicode data).
3

varchar(max)

Maximum length of 2E + 31 characters, Variable-length non-Unicode data (SQL Server 2005 only).
4

text

Variable-length non-Unicode data with a maximum length of 2,147,483,647 characters.

Unicode字符字符串数据类型

Sr.No. DATA TYPE & Description
1

nchar

Maximum length of 4,000 characters.( Fixed length Unicode)
2

nvarchar

Maximum length of 4,000 characters.(Variable length Unicode)
3

nvarchar(max)

Maximum length of 2E + 31 characters (SQL Server 2005 only).( Variable length Unicode)
4

ntext

Maximum length of 1,073,741,823 characters. ( Variable length Unicode )

二进制数据类型

Sr.No. DATA TYPE & Description
1

binary

Maximum length of 8,000 bytes(Fixed-length binary data )
2

varbinary

Maximum length of 8,000 bytes.(Variable length binary data)
3

varbinary(max)

Maximum length of 2E + 31 bytes (SQL Server 2005 only). ( Variable length Binary data)
4

image

Maximum length of 2,147,483,647 bytes. ( Variable length Binary Data)

杂项数据类型

Sr.No. DATA TYPE & Description
1

sql_variant

Stores values of various SQL Server-supported data types, except text, ntext, and timestamp.
2

timestamp

Stores a database-wide unique number that gets updated every time a row gets updated
3

uniqueidentifier

Stores a globally unique identifier (GUID)
4

xml

Stores XML data. You can store xml instances in a column or a variable (SQL Server 2005 only).
5

cursor

Reference to a cursor object
6

table

Stores a result set for later processing