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Hello and welcome to this comprehensive guide on functions in SQL Server. SQL Server has a vast collection of built-in functions that can help you manipulate and transform data in your database. In this article, we will explore the various functions available in SQL Server and provide you with examples to help you understand how to use them.

## What is a Function in SQL Server?

A function in SQL Server is a pre-defined piece of code that performs a specific task. Functions can be used to return a value or a table. They operate on one or more input values, which are known as parameters, and produce an output. Functions can be used in queries, views, stored procedures, and user-defined functions.

### Types of Functions in SQL Server

SQL Server has different types of functions that are used for different purposes. Here are the different types of functions available in SQL Server:

## Scalar Functions in SQL Server

A scalar function in SQL Server returns a single value based on its input parameters. Scalar functions can be used in queries, views, and stored procedures. Here are some of the most commonly used scalar functions in SQL Server:

### 1. ABS Function

The ABS function in SQL Server returns the absolute value of a numeric expression. The absolute value is the positive value of the input parameter. Here is an example of how to use the ABS function:

`SELECT ABS(-10) AS AbsoluteValue;`

AbsoluteValue |
---|

10 |

### 2. LEN Function

The LEN function in SQL Server returns the number of characters in a string expression. Here is an example of how to use the LEN function:

`SELECT LEN('Hello World!') AS StringLength;`

StringLength |
---|

12 |

### 3. UPPER and LOWER Functions

The UPPER function in SQL Server returns the input string in uppercase, while the LOWER function returns the input string in lowercase. Here are some examples of how to use the UPPER and LOWER functions:

`SELECT UPPER('hello world!') AS UpperCase;`

UpperCase |
---|

HELLO WORLD! |

`SELECT LOWER('HELLO WORLD!') AS LowerCase;`

LowerCase |
---|

hello world! |

## Table-Valued Functions in SQL Server

Table-valued functions in SQL Server return a table as their output. There are two types of table-valued functions: inline table-valued functions and multi-statement table-valued functions.

### 1. Inline Table-Valued Functions

An inline table-valued function in SQL Server is a single SELECT statement that returns a result set as a table. Here is an example of how to create an inline table-valued function:

`CREATE FUNCTION fn_GetProductByCategory (@CategoryId INT)`

RETURNS TABLE

AS

RETURN

(

SELECT ProductId, ProductName, UnitPrice

FROM Products

WHERE CategoryId = @CategoryId

);

The above function returns the products with a specified category id.

### 2. Multi-Statement Table-Valued Functions

A multi-statement table-valued function in SQL Server is a stored procedure that returns a table as its output. Here is an example of how to create a multi-statement table-valued function:

`CREATE FUNCTION fn_GetProductByCategory (@CategoryId INT)`

RETURNS @Products TABLE

(

ProductId INT,

ProductName VARCHAR(50),

UnitPrice DECIMAL(10, 2)

)

AS

BEGIN

INSERT INTO @Products

SELECT ProductId, ProductName, UnitPrice

FROM Products

WHERE CategoryId = @CategoryId

RETURN

END;

The above function returns the products with a specified category id.

## Aggregate Functions in SQL Server

Aggregate functions in SQL Server are used to perform calculations on a set of values and return a single value. Here are the aggregate functions available in SQL Server:

### 1. SUM Function

The SUM function in SQL Server returns the sum of all values in a specified column. Here is an example of how to use the SUM function:

`SELECT SUM(UnitPrice) AS TotalPrice`

FROM Products;

TotalPrice |
---|

440.00 |

### 2. AVG Function

The AVG function in SQL Server returns the average of all values in a specified column. Here is an example of how to use the AVG function:

`SELECT AVG(UnitPrice) AS AveragePrice`

FROM Products;

AveragePrice |
---|

12.57 |

### 3. MIN and MAX Functions

The MIN and MAX functions in SQL Server return the minimum and maximum values in a specified column, respectively. Here are some examples of how to use the MIN and MAX functions:

`SELECT MIN(UnitPrice) AS MinimumPrice`

FROM Products;

MinimumPrice |
---|

2.50 |

`SELECT MAX(UnitPrice) AS MaximumPrice`

FROM Products;

MaximumPrice |
---|

39.99 |

### FAQs

#### Q1. What is a function in SQL Server?

A function in SQL Server is a pre-defined piece of code that performs a specific task. Functions can be used to return a value or a table. They operate on one or more input values, which are known as parameters, and produce an output.

#### Q2. What are the different types of functions in SQL Server?

SQL Server has different types of functions that are used for different purposes. The different types of functions available in SQL Server are:

1. Scalar functions

2. Table-valued functions

a. Inline table-valued functions

b. Multi-statement table-valued functions

3. Aggregate functions

#### Q3. How can I create a function in SQL Server?

You can create a function in SQL Server using the CREATE FUNCTION statement. You need to specify the name of the function, input parameters, return type, and the code inside the function.

#### Q4. Can I use functions in queries, views, and stored procedures?

Yes, you can use functions in queries, views, and stored procedures. Functions are very useful in SQL because they allow you to reuse code and make your queries more concise and readable.

#### Q5. What are the most commonly used scalar functions in SQL Server?

Some of the most commonly used scalar functions in SQL Server are:

1. ABS function

2. LEN function

3. UPPER and LOWER functions

4. LEFT and RIGHT functions

5. REPLACE function

#### Q6. What is an aggregate function in SQL Server?

An aggregate function in SQL Server is used to perform calculations on a set of values and return a single value. Examples of aggregate functions are SUM, AVG, MIN, and MAX.

In conclusion, functions are an essential part of SQL Server and are used to perform various tasks. Scalar functions are used to return a single value, table-valued functions return a table as its output, and aggregate functions perform calculations on a set of values. By using functions, you can make your queries more efficient, concise, and readable. We hope that this guide has been helpful in understanding the different types of functions available in SQL Server and how to use them.