Data type of SQL Server database

There are three types of databases ： Digital data types 、 Character data type 、 Date and time data types .

One 、 Digital

I record several commonly used , Incomplete

Integer types	bigint	- ~ -1
	int	- ~  -1
	bit	1 or 0
Decimal type	decimal	These two usages are the same , Almost no difference ,numeric（52,1） This means that the total length is 52, The decimal places are 1 position . You can also leave it blank , Or just add a number to indicate the total length （ No decimal places ）
	numeric
	float	The most commonly used is still float
Type of currency	money	Ten thousandths of the unit of currency , However, it is generally used directly float That's OK

Two 、 Character data type

Single byte （8000）	varchar()	Lengthening , The maximum number of bytes that can be stored	At the expense of performance （ Judge every time ）, Save space	Commonly used varchar() type
	char()	Fixed length , The storage space is allocated directly	Wasted space , Improved performance
Double byte （4000）	nvarchar()	Lengthening		Commonly used nvarchar() type
	nchar()	Fixed length
A letter takes up a byte , A Chinese character takes up two bytes

3、 ... and 、 Date and time data types

datetime	Accurate to milliseconds
smalldatetime	To the minute
Generally, the date can also be in character type varchar() To represent the .