When working with SQL Server, it is important to understand the different datatypes available and how they can be used. In this article, we will explore the various datatypes in SQL Server and discuss their characteristics and best use cases.

Binary Datatypes

Binary datatypes are used to store binary data, such as hexadecimal values. There are two binary datatypes in SQL Server:

• BINARY: This datatype can store up to 8000 bytes of fixed-length binary data.
• VARBINARY: This datatype can store up to 8000 bytes of variable-length binary data.

It is recommended to use the VARBINARY datatype when you expect null values or variations in data size.

Character Datatypes

Character datatypes are used to store any combination of letters, symbols, and numbers. There are two character datatypes in SQL Server:

• CHAR: This datatype can store up to 8000 bytes of fixed-length character data.
• VARCHAR: This datatype can store up to 8000 bytes of variable-length character data.

Similar to binary datatypes, it is recommended to use the VARCHAR datatype when you expect null values or variations in data size.

Date and Time Datatypes

Date and time datatypes are used to store date and time values. There are two datetime datatypes in SQL Server:

• DATETIME: This datatype can store dates from January 1, 1753, to December 31, 9999, with an accuracy of 3.33 milliseconds.
• SMALLDATETIME: This datatype can store dates from January 1, 1900, to June 6, 2079, with an accuracy to the minute.

When not specifying the date or time portion of a datetime value, default values are supplied.

Numeric Datatypes

Numeric datatypes are used to store numeric values. There are two kinds of numeric datatypes in SQL Server:

• Exact Numeric Data: This datatype can store all decimal numbers with complete accuracy. Examples include DECIMAL and NUMERIC.
• Approximate Numeric Data: This datatype cannot store decimal numbers with complete accuracy. Examples include FLOAT and REAL.

Integer Datatypes

Integer datatypes are used to store whole numbers. There are three integer datatypes in SQL Server:

• TINYINT: This datatype can store integer values from 0 through 255.
• SMALLINT: This datatype can store integer values from -32768 through 32,767.
• INT: This datatype can store integer values from -2147483648 through 2147483647.

Monetary Datatypes

Monetary datatypes are used to store monetary values. There are two monetary datatypes in SQL Server:

• MONEY: This datatype can store monetary values within a specific range.
• SMALLMONEY: This datatype can store smaller monetary values within a specific range.

Special Datatypes

There are several special datatypes in SQL Server:

• BIT: This datatype is used for true/false or yes/no types of data.
• CURSOR: This datatype is used for variables or stored procedure OUTPUT parameters that contain a reference to a cursor.
• TIMESTAMP: This datatype is automatically updated every time a row containing a timestamp column is inserted or updated.
• UNIQUEIDENTIFIER: This datatype is used to store globally unique identifiers (GUIDs).

Text and Image Datatypes

Text and image datatypes are used to store large amounts of text or binary data. There are three datatypes in this category:

• TEXT: This datatype is used to store variable-length character data.
• NTEXT: This datatype is used to store variable-length Unicode character data.
• IMAGE: This datatype is used to store binary data, such as pictures.

Unicode Character Datatypes

Unicode character datatypes are used to store characters from various character sets. There are two Unicode character datatypes in SQL Server:

• NCHAR: This datatype can store fixed-length Unicode character data.
• NVARCHAR: This datatype can store variable-length Unicode character data.

It is recommended to use the NVARCHAR datatype when you expect null values or variations in data size.

User-Defined Datatypes

In addition to the built-in datatypes, SQL Server allows you to create your own user-defined datatypes. These datatypes can be based on existing SQL Server datatypes and can be used in CREATE TABLE or ALTER TABLE statements.

Understanding the different datatypes in SQL Server is crucial for designing efficient and accurate database schemas. By choosing the appropriate datatype for each column, you can ensure data integrity and optimize storage space.