Field data types
Numeric data types:
Integer data types: bigint, int, smallint, tinyint
decimal和numeric
muney and smalloney
float and real floating-point types
Character data types
Char (10) regardless of whether or not to store characters reach this length is 10 characters occupy space
Varchar (50) of variable length, although the statement 50 space, but he is not necessarily occupy 50 characters.
Text text type
Nchar
Nvarchar N at the beginning of all the characters unico
Ntext
Date and Time Types
Datetime 和smalldatetime
It indicates that the difference between two different time and date range, precision are different,
datetime to date 9999-12-31 1753-1-1 range, the accuracy of the time is 3.33 ms.
Smalldatetime 1900-1-1 date range to one minute time precision 2079-12-31
Binary type
Binary varbinay, image three data types
Binary for storing the number of fixed-length binary data,
Varbinary for storing binary data of variable length, the length of storage are both 1-8000
image data for storing image information of specific types
Specific data type
Native data type cursor, sql_variant, table, timestamp, uniqueidentifier, xml of six special purposes.
Temporary tables
Name of the local temporary table # symbol begins with a single number. Only the current user connection is visible. Global temporary table name begins with a double number sign ##, after you create are visible to any user
Create table #test
(id int not null
Name nvarchar(10) null,
Adress nvarchar(50) null
)
You may not see the temporary tables in Object Explorer, but you can use a query to select.
The difference between check constraints and rules
check constraint is created in the create table statement indicates that the specified, and rules need to be used as a separate database objects
Only one rule on one, but you can use multiple check constraints
Rules can be applied to multiple columns, can also be applied to user-defined data types, check constraints can only be used in his column
Create a rule: create rule rule name as the value of the expression
Create rule sorce as @value between 0 and 100 to create a rule
Sp_bindrule sorce, 'grade information, scores' constraint bound to a concrete column
Cancellation and delete rules
Rules should be lifted dependence
Futureonly represents the binding is released when the objectname is null type in a user-defined current value, if an error when it is released futureonly
Delete Rule
Drop rule sorce
Unbind
Sp_unbindrule 'achievement information, fraction'
