10 SQL Server Functions Every Dev Should Know

Hello Dev, welcome to this comprehensive guide on SQL server functions. In this article, we’re going to take a deep dive into 10 essential SQL server functions that every developer should know. Whether you’re just getting started with SQL, or you’re a seasoned developer, you’re sure to learn something new.

1. What Are SQL Server Functions?

Before we dive into the specifics, let’s take a moment to define what SQL server functions are. In short, a SQL server function is a pre-built set of code that can be used to perform a specific action on a SQL database. Functions can be used to manipulate data, perform calculations, and much more.

SQL server functions can be divided into two main categories: built-in functions and user-defined functions (UDFs). Built-in functions are pre-defined by SQL Server, and can be used by any developer. UDFs, on the other hand, are created by developers for their specific needs.

Built-In Functions

SQL Server includes a wide variety of built-in functions that can be used to manipulate data. These functions are divided into different categories depending on the type of operation they perform. Some of the most commonly used built-in functions include:

Function	Description
Aggregate Functions	Perform calculations on multiple rows of data
Date/Time Functions	Perform calculations on dates and times
String Functions	Manipulate character strings
Mathematical Functions	Perform mathematical calculations
Conversion Functions	Convert data from one format to another

User-Defined Functions

While built-in functions are useful, they may not always meet the specific needs of a developer. This is where user-defined functions (UDFs) come in. UDFs are created by developers to perform a specific task that is not included in the built-in library.

UDFs can be created in two different ways: scalar UDFs and table-valued UDFs. Scalar UDFs return a single value, while table-valued UDFs return a table. UDFs are created using T-SQL code, and can be called from any other T-SQL code block.

2. The Top 10 SQL Server Functions Every Dev Should Know

Now that we know a bit more about SQL Server functions, let’s dive into the top 10 functions that every developer should know.

2.1 COUNT()

The COUNT() function is a built-in SQL Server function that is used to count the number of rows in a table. This function can be used with or without a WHERE clause to filter the results.

For example, let’s say we have a table called “employees” with the following rows:

Name	Department
John	Marketing
Jane	Marketing
Bob	Engineering

If we wanted to count the total number of employees in the “employees” table, we could use the following SQL code:

COUNT(*) FROM employees

This would return the result “3”, since there are three rows in the “employees” table.

2.2 SUM()

The SUM() function is used to calculate the sum of a column in a table. This function can be used with or without a WHERE clause to filter the results.

For example, let’s say we have a table called “sales” with the following rows:

Month	Sales
January	1000
February	1500
March	2000

If we wanted to calculate the total sales for the year, we could use the following SQL code:

SUM(sales) FROM sales

This would return the result “4500”, since the total sales for the year are 4500.

2.3 MAX()

The MAX() function is used to find the maximum value in a column in a table. This function can be used with or without a WHERE clause to filter the results.

For example, let’s say we have a table called “products” with the following rows:

Name	Price
Product 1	10.99
Product 2	15.99
Product 3	12.99

If we wanted to find the most expensive product in the “products” table, we could use the following SQL code:

MAX(price) FROM products

This would return the result “15.99”, since that is the price of the most expensive product.

2.4 MIN()

The MIN() function is used to find the minimum value in a column in a table. This function can be used with or without a WHERE clause to filter the results.

For example, let’s say we have a table called “products” with the following rows:

Name	Price
Product 1	10.99
Product 2	15.99
Product 3	12.99

If we wanted to find the least expensive product in the “products” table, we could use the following SQL code:

MIN(price) FROM products

This would return the result “10.99”, since that is the price of the least expensive product.

2.5 AVG()

The AVG() function is used to find the average value of a column in a table. This function can be used with or without a WHERE clause to filter the results.

For example, let’s say we have a table called “sales” with the following rows:

Month	Sales
January	1000
February	1500
March	2000

If we wanted to find the average monthly sales for the year, we could use the following SQL code:

AVG(sales) FROM sales

This would return the result “1500”, since the average monthly sales for the year are 1500.

2.6 LEN()

The LEN() function is used to find the length of a string. This function can be used with or without a WHERE clause to filter the results.

For example, let’s say we have a table called “employees” with the following rows:

Name	Email
John	john@example.com
Jane	jane@example.com
Bob	bob@example.com

If we wanted to find the length of each employee’s email address, we could use the following SQL code:

LEN(email) FROM employees

This would return the length of each email address in the table.

2.7 UPPER()

The UPPER() function is used to convert a string to uppercase. This function can be used with or without a WHERE clause to filter the results.

For example, let’s say we have a table called “products” with the following rows:

Name	Description
Product 1	This is the description for product 1.
Product 2	This is the description for product 2.
Product 3	This is the description for product 3.

If we wanted to convert each product description to uppercase, we could use the following SQL code:

UPPER(description) FROM products

This would return the uppercase version of each product description in the table.

2.8 LOWER()

The LOWER() function is used to convert a string to lowercase. This function can be used with or without a WHERE clause to filter the results.

For example, let’s say we have a table called “products” with the following rows:

Name	Description
Product 1	THIS IS THE DESCRIPTION FOR PRODUCT 1.
Product 2	THIS IS THE DESCRIPTION FOR PRODUCT 2.
Product 3	THIS IS THE DESCRIPTION FOR PRODUCT 3.

If we wanted to convert each product description to lowercase, we could use the following SQL code:

LOWER(description) FROM products

This would return the lowercase version of each product description in the table.

2.9 DATEPART()

The DATEPART() function is used to extract a specific part of a date, such as the year, month, or day. This function can be used with or without a WHERE clause to filter the results.

For example, let’s say we have a table called “orders” with the following rows:

Order ID	Date
1	2019-01-01
2	2019-02-01
3	2019-03-01

If we wanted to extract the year from each order date, we could use the following SQL code:

DATEPART(year, date) FROM orders

This would return the year of each order date.

2.10 CONCAT()

The CONCAT() function is used to concatenate two or more strings together. This function can be used with or without a WHERE clause to filter the results.

For example, let’s say we have a table called “employees” with the following rows:

First Name	Last Name
John	Doe
Jane	Smith
Bob	Johnson

If we wanted to create a new column that concatenated the first and last names, we could use the following SQL code:

CONCAT(first_name, ' ', last_name) AS full_name FROM employees

This would return a new column called “full_name” that contained the concatenated first and last names of each employee.

3. Conclusion

SQL Server functions are an essential part of any developer’s toolkit. Whether you’re just getting started with SQL, or you’re a seasoned developer, knowing how to use these functions can save you time and effort, and lead to more efficient and effective code.

3.1 FAQ

Q: Are SQL Server functions case-sensitive?

A: No, SQL Server functions are not case-sensitive. You can use uppercase or lowercase letters interchangeably.

Q: Can I create my own SQL Server functions?

A: Yes, you can create your own SQL Server functions using T-SQL code.

Q: Can SQL Server functions be used with other databases?

A: No, SQL Server functions are specific to SQL Server and cannot be used with other databases.

Q: Are there any performance considerations when using SQL Server functions?

A: Yes, some SQL Server functions can be slow when used with large datasets. It’s important to test your code and optimize it as needed to ensure good performance.