Welcome Dev, as a developer, you must have come across the term SQL Server Data Types. Data types are an important aspect of any programming language. In SQL Server, data types are used to define the type of data that can be stored in a column or variable. It is important to understand the different data types available in SQL Server to ensure that your database is designed for optimal storage and retrieval of data. In this article, we will discuss the different SQL Server data types and their usage.
What are SQL Server Data Types?
Data types in SQL Server are used to define the type of data that can be stored in a column or variable. In other words, data types specify the kind of values that can be assigned to a variable. SQL Server provides a wide range of data types to accommodate different types of data.
Numeric Data Types
Numeric data types are used to store numbers in SQL Server. There are different types of numeric data types available in SQL Server as shown in the table below:
Data Type |
Description |
|---|---|
INT |
Stores whole numbers (positive or negative) with a maximum length of 4 bytes. |
BIGINT |
Stores whole numbers (positive or negative) with a maximum length of 8 bytes. |
DECIMAL/NUMERIC |
Stores exact numbers with a maximum precision of 38 digits. |
FLOAT |
Stores floating-point values with a maximum length of 8 bytes. |
REAL |
Stores floating-point values with a maximum length of 4 bytes. |
SMALLINT |
Stores whole numbers (positive or negative) with a maximum length of 2 bytes. |
TINYINT |
Stores whole numbers (positive or negative) with a maximum length of 1 byte. |
INT: INT is a data type used to store whole numbers (positive or negative) with a maximum length of 4 bytes. An example of INT data type is:
SELECT Quantity FROM Orders WHERE OrderID = 10248
This query will return the quantity of product in order 10248.
BIGINT: BIGINT is a data type used to store whole numbers (positive or negative) with a maximum length of 8 bytes. An example of BIGINT data type is:
SELECT COUNT(*) FROM Customers
This query will return the total number of customers in the database.
DECIMAL/NUMERIC: DECIMAL/NUMERIC is a data type used to store exact numbers with a maximum precision of 38 digits. An example of DECIMAL/NUMERIC data type is:
SELECT Price FROM Products WHERE ProductID = 3
This query will return the price of the product with ID 3.
FLOAT: FLOAT is a data type used to store floating-point values with a maximum length of 8 bytes. An example of FLOAT data type is:
SELECT AVG(Price) FROM Products
This query will return the average price of all the products in the database.
REAL: REAL is a data type used to store floating-point values with a maximum length of 4 bytes. An example of REAL data type is:
SELECT MAX(Quantity) FROM Orders
This query will return the maximum quantity ordered in any order.
SMALLINT: SMALLINT is a data type used to store whole numbers (positive or negative) with a maximum length of 2 bytes. An example of SMALLINT data type is:
SELECT COUNT(*) FROM Products WHERE CategoryID = 2
This query will return the total number of products in category 2.
TINYINT: TINYINT is a data type used to store whole numbers (positive or negative) with a maximum length of 1 byte. An example of TINYINT data type is:
SELECT * FROM Employees WHERE Salary < 30000
This query will return all employees with a salary less than 30,000.
Character Data Types
Character data types are used to store alphanumeric data in SQL Server. There are different types of character data types available in SQL Server as shown in the table below:
Data Type |
Description |
|---|---|
CHAR |
Stores fixed-length character strings with a maximum length of 8,000 characters. |
VARCHAR |
Stores variable-length character strings with a maximum length of 8,000 characters. |
TEXT |
Stores variable-length character strings with a maximum length of 2^31-1 (2,147,483,647) characters. |
CHAR: CHAR is a data type used to store fixed-length character strings with a maximum length of 8,000 characters. An example of CHAR data type is:
SELECT CustomerName FROM Customers WHERE CustomerID = 'ALFKI'
This query will return the name of the customer with ID ALFKI.
VARCHAR: VARCHAR is a data type used to store variable-length character strings with a maximum length of 8,000 characters. An example of VARCHAR data type is:
SELECT ProductName FROM Products WHERE ProductID = 5
This query will return the name of the product with ID 5.
TEXT: TEXT is a data type used to store variable-length character strings with a maximum length of 2^31-1 (2,147,483,647) characters. An example of TEXT data type is:
SELECT Notes FROM Orders WHERE OrderID = 10248
This query will return the notes for order 10248.
Date and Time Data Types
Date and time data types are used to store date and time values in SQL Server. There are different types of date and time data types available in SQL Server as shown in the table below:
Data Type |
Description |
|---|---|
DATE |
Stores dates only, with no time portion. |
DATETIME |
Stores both date and time values with a precision of one three-hundredth of a second. |
SMALLDATETIME |
Stores both date and time values with a precision of one minute. |
TIME |
Stores time values with a precision of one hundred nanoseconds. |
DATE: DATE is a data type used to store dates only, with no time portion. An example of DATE data type is:
SELECT BirthDate FROM Employees WHERE EmployeeID = 1
This query will return the birth date of the employee with ID 1.
DATETIME: DATETIME is a data type used to store both date and time values with a precision of one three-hundredth of a second. An example of DATETIME data type is:
SELECT OrderDate FROM Orders WHERE CustomerID = 'ALFKI'
This query will return the order date for all orders made by customer ALFKI.
SMALLDATETIME: SMALLDATETIME is a data type used to store both date and time values with a precision of one minute. An example of SMALLDATETIME data type is:
SELECT HireDate FROM Employees WHERE EmployeeID = 2
This query will return the hire date of the employee with ID 2.
TIME: TIME is a data type used to store time values with a precision of one hundred nanoseconds. An example of TIME data type is:
SELECT CAST(GETDATE() AS TIME) AS CurrentTime
This query will return the current time.
Other Data Types
Other data types available in SQL Server include:
Data Type |
Description |
|---|---|
BIT |
Stores 0, 1, or NULL values. |
GEOGRAPHY |
Stores geospatial data in a geography data type. |
IMAGE |
Stores variable-length binary data with a maximum length of 2^31-1 (2,147,483,647) bytes. |
MONEY |
Stores monetary values with a maximum precision of 19 digits. |
XML |
Stores XML data. |
BIT: BIT is a data type used to store 0, 1, or NULL values. An example of BIT data type is:
SELECT IsActive FROM Customers WHERE CustomerID = 'ALFKI'
This query will return whether the customer with ID ALFKI is active or not.
GEOGRAPHY: GEOGRAPHY is a data type used to store geospatial data in a geography data type. An example of GEOGRAPHY data type is:
SELECT * FROM Locations WHERE Location.STDistance(@myLocation) < 1000
This query will return all locations within a distance of 1000 meters from my location.
IMAGE: IMAGE is a data type used to store variable-length binary data with a maximum length of 2^31-1 (2,147,483,647) bytes. An example of IMAGE data type is:
SELECT Picture FROM Products WHERE ProductID = 2
This query will return the picture of the product with ID 2.
MONEY: MONEY is a data type used to store monetary values with a maximum precision of 19 digits. An example of MONEY data type is:
SELECT AVG(UnitPrice) FROM Products WHERE CategoryID = 1
This query will return the average unit price of all products in category 1.
XML: XML is a data type used to store XML data. An example of XML data type is:
SELECT ProductDescription FROM Products WHERE ProductID = 3 FOR XML AUTO
This query will return the product description of the product with ID 3 in XML format.
Conclusion
In this article, we discussed the different SQL Server data types and their usage. It is important to understand the different data types available in SQL Server to ensure that your database is designed for optimal storage and retrieval of data. With this knowledge, you can design your database schema and queries to efficiently handle the data and maximize performance.
FAQs
Q. What is a data type?
A data type is an attribute that specifies the type of data that can be stored in a variable or column.
Q. Why are data types important?
Data types are important because they ensure that the right kind of data is stored in a variable or column, which helps to ensure data integrity and prevent errors.
Q. How do I choose the right data type for my column?
You should choose a data type that can accommodate the range of values that will be stored in the column. For example, if you are storing whole numbers that will not exceed 2 billion, you can use the INT data type.
Q. Can I change the data type of a column?
Yes, you can change the data type of a column using the ALTER TABLE statement. However, you should be careful when changing data types because it can cause data loss or unexpected behavior.
Q. What is the difference between CHAR and VARCHAR?
CHAR is a fixed-length character string while VARCHAR is a variable-length character string. This means that CHAR always allocates the same amount of storage space while VARCHAR allocates only the amount of space needed to store the data.
Q. What is the difference between DATE and DATETIME?
DATE stores only the date while DATETIME stores both the date and time values with a precision of one three-hundredth of a second.