SQL Server Data Types Overview
Data types are an essential aspect of database design. They describe the type of data that can be stored in a column, variable, or parameter.
SQL Server provides a range of data types suitable for different situations. In this article, we explore the various SQL Server data types, their characteristics, and usage.
List of SQL Server Data Types
SQL Server offers various data types, such as numeric, character string, binary string, date & time, and other data types. Here’s a brief overview of these data types:
Numeric data types:
- Bit – Represents 0 or 1 values.
- Int – Stores whole numbers within the range of -2,147,483,648 to 2,147,483,647.
- Bigint – Stores large whole numbers within the range of -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807.
- Smallint – Stores small whole numbers within the range of -32,768 to 32,767.
- Tinyint – Stores small whole numbers within the range of 0 to 255.
- Decimal – Stores exact numeric values with a fixed precision and scale.
- Numeric – Stores exact numeric values with a fixed precision and scale.
- Money – Stores monetary values with a precision of up to four decimal places.
- Smallmoney – Stores monetary values with a precision of up to four decimal places.
Character string data types:
- Char – Stores fixed-length strings of up to 8,000 characters.
- Varchar – Stores variable-length strings of up to 8,000 characters.
- Text – Stores variable-length character data with a maximum length of 2^31-1 (or 2,147,483,647).
- Nchar – Stores fixed-length Unicode strings of up to 4,000 characters.
- Nvarchar – Stores variable-length Unicode strings of up to 4,000 characters.
- Ntext – Stores variable-length Unicode character data with a maximum length of 2^30-1 (or 1,073,741,823).
Binary string data types:
- Binary – Stores fixed-length binary data of up to 8,000 bytes.
- Varbinary – Stores variable-length binary data of up to 8,000 bytes.
- Image – Stores variable-length binary data with a maximum length of 2^31-1 (or 2,147,483,647).
Date and time data types:
- Date – Stores dates from January 1, 0001 to December 31, 9999.
- Time – Stores time values with a precision of up to seven digits.
- Datetime – Stores date and time values between January 1, 1753 and December 31, 9999.
- Datetime2 – Stores date and time values with a precision of up to 7 digits.
- Datetimeoffset – Stores date and time values with a time zone offset.
Other data types:
- Xml – Stores XML data.
- Timestamp – Stores a unique value for each row that’s updated automatically each time the row is modified.
- Uniqueidentifier – Stores a 16-byte GUID.
Future Removal of Ntext, Text, and Image Data Types
The ntext, text, and image data types have been deprecated in SQL Server since 2005 in favor of nvarchar(max), varchar(max), and varbinary(max) respectively.
While these deprecated data types continue to work, Microsoft has announced that they’ll be removed in a future version of SQL Server. As such, it’s recommended to use the newer data types instead.
Exact Numeric Data Types
Exact numeric data types store precise numbers with no decimal or rounding errors. Here’s a brief overview of the various exact numeric data types:
Bit:
The bit data type stores boolean data as either a 0 or 1 value.
It’s mainly used for representing binary values such as true/false, yes/no, on/off, and so on. This data type consumes one byte of storage.
Int, Bigint, Smallint, Tinyint:
The integer data types store whole numbers with no decimal places. The int data type stores whole numbers within the range of -2,147,483,648 to 2,147,483,647, while bigint stores large whole numbers within the range of -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807.
Smallint stores small whole numbers within the range of -32,768 to 32,767, while tinyint stores small whole numbers within the range of 0 to 255. Depending on the data type, they consume 2 to 8 bytes of storage.
Decimal, Numeric:
The decimal and numeric data types represent exact numeric values with a fixed precision and scale. Decimal and numeric are interchangeable and can store up to 38 digits of precision and up to 38 digits of scale.
They consume up to 17 bytes of storage.
Money, Smallmoney:
The money and smallmoney data types are used for storing monetary values up to four decimal places.
Money can store values within the range of -922,337,203,685,477.5808 to +922,337,203,685,477.5807, while smallmoney can store values within the range of -214,748.3648 to 214,748.3647. Depending on the data type, they consume 4 to 8 bytes of storage.
Memory Usage and Range of Values
Each data type has its own range of values that can be stored and consumes a specific amount of memory. When designing a database, it’s important to choose an appropriate data type that meets the particular requirements of the data being stored.
Choosing the wrong data type can lead to wasted memory, reduced performance, and possible data loss.
Conclusion
Data types and their characteristics are an essential aspect of database design. SQL Server provides a variety of data types suitable for different scenarios.
In this article, we’ve explored the SQL Server data types, including numeric, character string, binary string, date & time, and other data types. Additionally, we’ve looked at the exact numeric data types and their memory usage and range of values.
As database designers, it’s important to choose the correct data type appropriately to improve database efficiency and performance.
3) Approximate Numeric Data Types
In addition to exact numeric data types, SQL Server also provides approximate numeric data types that store floating-point numeric data. These data types are ideal for storing numbers with fractional components where exact precision is not required.
Here’s an overview of the two approximate numeric data types in SQL Server:
Float(n):
The float(n) data type stores both floating-point and real numbers. The n parameter specifies the precision of the float number, which ranges from 1 to 53.
The float data type is used to store large numbers with decimal places and requires 4 to 8 bytes of storage. The precision of float data is not fixed, so it may not be appropriate for applications that require exact numeric precision.
Real:
The real data type stores floating-point numbers with a precision of approximately 7 digits. The real data type takes up 4 bytes of storage and is designed for compatibility with existing systems.
Approximate numeric data types are useful in situations where precision is not critical. These data types have a range of values that can be stored and consume a specific amount of memory.
4) Date & Time Data Types
In addition to numeric data types, SQL Server also provides a range of date and time data types. These data types are used to store date, time, and time zone data.
Here’s an overview of the date and time data types in SQL Server:
Datetime:
The datetime data type stores values that include both date and time. The supported range of datetime data is from January 1, 1753, through December 31, 9999.
The accuracy of this data type is rounded to increments of .000, .003, or .007 seconds, and it consumes eight bytes of storage.
Smalldatetime:
The smalldatetime data type stores values that include both date and time.
The supported range of smalldatetime data is from January 1, 1900, through June 6, 2079. The accuracy of this data type is rounded to increments of 1 minute, and it consumes four bytes of storage.
Date:
The date data type stores values that represent a specific date. The supported range of date data is from January 1, 0001, through December 31, 9999.
The date data type is useful for storing dates without time components, and it consumes three bytes of storage.
Time:
The time data type stores values that represent a specific time.
The supported range of time data is from 00:00:00.0000000 through 23:59:59.9999999. Time data is useful for storing time without the date component, and it consumes three to five bytes of storage.
Datetimeoffset:
The datetimeoffset data type stores values that include both date, time, and time zone offset. The supported range of datetimeoffset data is from January 1, 1753, through December 31, 9999.
The data type’s accuracy is rounded to increments of .000, .003, or .007 seconds, and it consumes ten bytes of storage.
Datetime2:
The datetime2 data type is similar to datetime, but it provides a higher level of precision.
The data type stores values that include both date and time, and the supported range of datetime2 data is from January 1, 0001, through December 31, 9999. This data type’s accuracy is rounded to increments of .0000001 seconds, and it consumes between six and eight bytes of storage.
Date and time data types are useful for storing temporal data and simplifying data manipulation. The choice of date and time data type depends on the nature of the data to be stored and the required level of precision.
Conclusion
In conclusion, SQL Server provides a range of data types suitable for different scenarios. These data types include numeric, character string, binary string, date & time, and other data types.
Additionally, SQL Server provides both exact and approximate numeric data types that store precise and approximated floating-point numeric data, respectively. Finally, date and time data types in SQL Server are ideal for storing temporal data and simplifying data manipulation.
When designing a database, it’s essential to choose appropriate data types that meet the particular requirements of the data being stored.
5) Character String Data Types
In any database, character string data types are essential for storing textual or string data. SQL Server provides different character string data types suited to different requirements.
In this section, we’ll take a closer look at character string data types in SQL Server.
Char:
The char data type is used to store fixed-length character strings of up to 8,000 characters.
If the data inserted into a char column is shorter than the defined length, it will be padded with spaces to reach the fixed length. As such, this data type consumes the full space, even if the string is shorter.
Varchar:
The varchar data type is used to store variable-length character strings of up to 8,000 characters. If the data inserted into a varchar column is shorter than the defined length, it only uses the space required for the actual string length.
This data type is better suited for storing text data that varies in length.
Varchar(max):
The varchar(max) data type is similar to the varchar data type but can store up to 2^31-1 characters.
It is available since SQL Server 2005 and is useful for storing large text-based data such as XML data.
Text:
The text data type stores variable-length character data with a maximum length of 2^31-1 (or 2,147,483,647).
This data type is useful when storing large text-based data such as articles, blog posts, comments, or reviews.
Unicode Character String Data Types:
SQL Server provides character string data types that support both Unicode and non-Unicode data.
Unicode is a standard encoding format that uses 16-bit characters to store a broad range of characters and their different representations in various languages globally. The following are Unicode character string data types in SQL Server:
Nchar:
The nchar data type is used to store fixed-length Unicode character strings of up to 4,000 characters.
Nvarchar:
The nvarchar data type is used to store variable-length Unicode character strings of up to 4,000 characters.
Ntext:
The ntext data type stores variable-length Unicode character data with a maximum length of 2^30-1 (or 1,073,741,823).
Non-Unicode Character String Data Types:
SQL Server also provides non-Unicode character string data types that do not support data from all languages. These character string data types are the following:
Char:
The char data type is used to store fixed-length non-Unicode character strings of up to 8,000 characters.
Varchar:
The varchar data type is used to store variable-length non-Unicode character strings of up to 8,000 characters.
Text:
The text data type stores variable-length non-Unicode character data with a maximum length of 2^31-1 (or 2,147,483,647).
The SQL Server allows developers to choose the appropriate character string data type based on the requirements, the length of text, performance, and storage limitations.
6) Binary String Data Types
In SQL Server, binary data types are used to store fixed-length and variable-length binary data. Binary data is any data that cannot be represented in a text format such as images, videos, audio, or executable files.
SQL Server provides three binary data types.
Binary:
The binary data type stores fixed-length binary data of up to 8,000 bytes.
If the data inserted into a binary column is shorter than the defined length, it will be padded with nulls to reach the full length.
Varbinary:
The varbinary data type stores variable-length binary data of up to 8,000 bytes.
If the data inserted into a varbinary column is shorter than the defined length, it will only use the space required for the actual binary data length.
Image:
The image data type stores variable-length binary data with a maximum length of 2^31-1 (or 2,147,483,647), ideal for storing large binary data such as images, audio, or video.
The binary string data types are essential in SQL server, as they offer a way to store large packets of data in a single field.
Conclusion
In conclusion, SQL Server provides different data types for handling character and binary strings data. The options allow for the storage of text and binary data in a manner that is appropriate and tidy for the particular situation.
The data types include fixed-length, variable-length, Unicode, and non-Unicode data type with their respective limits and representation methods. The use of appropriate data types for character and binary strings data essential when designing a database in terms of performance, scalability, and storage optimization.
7) Other Data Types
Apart from the numeric, character string, and binary string data types, SQL Server offers several other data types with unique characteristics. Here’s an overview of the various other data types in SQL Server:
Cursor:
The cursor data type is used for retrieving data from the database.
It allows developers to define a pointer to a database object (such as a table or view) and iterate through the rows of data one at a time.
Cursors are useful when you need to process data row by row, but they can be less efficient than using set-based operations.
Table:
The table data type allows you to store a collection of rows and columns. Each row represents a record, and each column represents a field or attribute.
The table data type is the foundation of relational databases, providing a structured way to store and manage data.
Variant:
The variant data type can store values of different data types. It’s flexible, but it can be less efficient than using specific data types.
The variant data type is often used in situations where the data type is not known in advance.
Sql_Variant:
The sql_variant data type is similar to the variant data type, but it’s designed for use in stored procedures and functions.
It allows you to pass values of different data types to stored procedures and functions without having to specify the data type explicitly.
User-Defined Data Types:
SQL Server allows you to define your own custom data types. This can be useful for representing complex data structures or for enforcing specific data validation rules.
User-defined data types can be based on existing SQL Server data types or on other user-defined data types.
Conclusion
In conclusion, SQL Server offers a comprehensive set of data types that cater to various data storage needs. From numeric and character string types to binary data and temporal values, SQL Server provides flexibility and efficiency in managing diverse data structures.
Understanding and utilizing appropriate data types is crucial for database design, ensuring performance, scalability, and data integrity.