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SQL data type

2022-04-22 09:41:00 【I just learned programming】

SQL A data type is an attribute , It specifies anything SQL The type of data in the object . stay SQL in , Any column 、 Variables or expressions have their data types .

When creating a table , You will use these data types . You should choose the appropriate data type for each column in the table as needed .

SQL Server Six data types are provided for you to use ：

Exact numeric data type

data type	Lower limit	ceiling
bigint	-9,223,372,036,854,770,000	9,223,372,036,854,770,000
int	-2,147,483,648	2,147,483,647
smallint	-32,768	32,767
tinyint	0	255
bit	0	1
decimal	1E+38	10^38 -1
numeric	1E+38	10^38 -1
money	-922,337,203,685,477.00	922,337,203,685,477.00
smallmoney	-214,748.36	214,748.36

Approximate numerical data type

data type	Lower limit	ceiling
float	-1.79E + 308	1.79E + 308
real	-3.40E + 38	3.40E + 38

Date and time data types

data type	Lower limit	ceiling
datetime	Jan 1, 1753	31-Dec-99
smalldatetime	1-Jan-00	6-Jun-79
date	Store a date data , for example June 30, 1991
time	Store a time data , for example 12:30 P.M.

Be careful ：datetime The time and accuracy are 3.33 ms, and smalldatetime The time accuracy of is 1 min.

String data type

data type	Lower limit	ceiling
char	char	Maximum length is 8,000 character .（ Fixed length is not Unicode character ）
varchar	varchar	Maximum length is 8,000 character .（ Lengthening is not Unicode data ）
varchar(max)	varchar(max)	Maximum length is 231 character , Lengthening is not Unicode data ( Limited to SQL Server 2005).
text	text	Lengthening is not Unicode Character data , Maximum length 2,147,483,647 character .

Unicode String data type

data type	describe
nchar	Maximum length 4000 character .（ Fixed length Unicode character string ）
nvarchar	Maximum length 4000 character .（ Lengthening Unicode character string ）
nvarchar(max)	Maximum length 231 character .（ Limited to SQL Server 2005）.（ Lengthening Unicode character string ）
ntext	Maximum length 1,073,741,823 character .（ Lengthening Unicode character string ）

Binary data type

data type	describe
binary	Maximum length 8000 byte .（ Fixed length binary data ）
varbinary	Maximum length 8000 byte .（ Variable length binary data ）
varbinary(max)	Maximum length 231 byte （ Limited to SQLServer 2005）. （ Variable length binary data ）
image	Maximum length 2,147,483,647 byte .（ Variable length binary data ）

Other data types

data type	describe
sql_variant	Store a variety of SQL Supported data types ,text、ntext、timestamp With the exception of .
timestamp	A unique value at the database level , This data is updated whenever a row is updated .
uniqueidentifier	Globally unique identifier （GUID）
xml	Storage XML data . You can store... In columns or variables XML example .（ Limited to SQL Server 2005）
cursor	Point to cursor object .
table	Store results , For later use .