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Author Topic: SQL Server 2000 Data Types  (Read 1329 times)

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SQL Server requires that each variable and column in a table should be defined with respect to the type of data it will store. From a bit to a huge image and binary storage types, the allocation is supposed to help the user conform to the data required, and help the engine allocate space and processing speed efficiently.

Built-in data types

SQL Server 2000 recognizes the following built in data types:

Data Types
 Description
 
bigint
 Integer data from -2^63 through 2^63-1
 
int
 Integer data from -2^31 through 2^31 - 1
 
smallint
 Integer data from -2^15 through 2^15 - 1
 
tinyint
 Integer data from 0 through 255
 
bit
 Integer data with either a 1 or 0 value
 
decimal
 Fixed precision and scale numeric data from -10^38 +1 through 10^38 -1
 
numeric
 Fixed precision and scale numeric data from -10^38 +1 through 10^38 -1
 
money
 Monetary data values from -2^63 through 2^63 - 1
 
smallmoney
 Monetary data values from -214,748.3648 through +214,748.3647
 
float
 Floating precision number data from -1.79E + 308 through 1.79E + 308
 
real
 Floating precision number data from -3.40E + 38 through 3.40E + 38
 
datetime
 Date and time data from January 1, 1753, through December 31, 9999,
with an accuracy of 3.33 milliseconds
 
smalldatetime
 Date and time data from January 1, 1900, through June 6, 2079,
with an accuracy of one minute
 
char
 Fixed-length character data with a maximum length of 8,000 characters
 
varchar
 Variable-length data with a maximum of 8,000 characters
 
text
 Variable-length data with a maximum length of 2^31 - 1 characters
 
nchar
 Fixed-length Unicode data with a maximum length of 4,000 characters
 
nvarchar
 Variable-length Unicode data with a maximum length of 4,000 characters
 
ntext
 Variable-length Unicode data with a maximum length of 2^30 - 1 characters
 
binary
 Fixed-length binary data with a maximum length of 8,000 bytes
 
varbinary
 Variable-length binary data with a maximum length of 8,000 bytes
 
image
 Variable-length binary data with a maximum length of 2^31 - 1 bytes
 
cursor
 A reference to a cursor
 
sql_variant
 A data type that stores values of various data types,
except text, ntext, timestamp, and sql_variant
 
table
 A special data type used to store a result set for later processing
 
timestamp
 A database-wide unique number that gets updated every time
a row gets updated
 
uniqueidentifier
 A globally unique identifier
 


Bigint, sql_variant, and table are new to SQL Server 2000

User-defined data types
You can make user-defined data types too, which sometimes can be more descriptive of the value types held in the object. This may make it easier for the programmer to document and work with the data. These data types are based on the built in types, and can be outfitted with preprogrammed defaults, checks, constraints, etc. . To create a user-defined data type, use

sp_addtype datatypename, basedatatype, ‘NULL'/'NOT NULL'

 

How to choose the appropriate data type
SQL Server stores data in data pages that are 8Kb (8192 bytes) in size. The system uses some of that s Sometimes, the system uses only 8060 bytes are availableto that are available to store user's data. Consider the size of a row of data in your tables. If the rows are large, make sure that multiples of the fit conveniently on a data page so that page space is not wasted. This is cut down on disk paging overhead when accessing the data. You want to maximize the number of rows of data which that will fit on a page. This can be accomplished both by splitting the tables, and by choosing the smallest data type which that will accommodate your data. .

In you are using integer data, data; consider that the tinyint datatype will accommodate data which that will fit into one byte of storage. So if the range of all of the data in your field (or variable) is between 0 and 255, use the tinyint datatype. If the range is between -32,768 and 32,767, use the smallint data type. And if If you need to store integer data from -2,147,483,648 through 2,147,483,647, use int data type.

Similarly with smallmoney. If smallmoney. if your value range is between -214748.3648 and 214,748.3647, use the smallmoney datatype.

Use smalldatetime data type instead of datetime data type, if you need to store the date and time data from January 1, 1900 through June 6, 2079, with accuracy to the minute.

Prefer varchar.nvarchar to text/ntext whenever possible because the text and image fields are stored separately, which produces additional paging. And prefer char/varchar to nchar/nvarchar data types because the n types require twice as much storage space. The n types are used primarily for unicode data.


 

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