3-6 SQL Functions Explained

Key Concepts

• Aggregate Functions
• Scalar Functions
• Date and Time Functions

Aggregate Functions

Aggregate functions in SQL perform calculations on a set of values and return a single value. Common aggregate functions include SUM, AVG, COUNT, MIN, and MAX.

Example: To find the total sales amount from a "Sales" table, you would use the following SQL command:

        SELECT SUM(SalesAmount) AS TotalSales
        FROM Sales;
    

Analogy: Think of aggregate functions as a calculator that summarizes a list of numbers into a single value, such as finding the total sum or average.

Scalar Functions

Scalar functions in SQL operate on a single value and return a single value. Common scalar functions include UPPER, LOWER, LEN, and ROUND.

Example: To convert a string to uppercase in a "Customers" table, you would use the following SQL command:

        SELECT UPPER(CustomerName) AS UppercaseName
        FROM Customers;
    

Analogy: Think of scalar functions as tools that transform individual pieces of data, like converting text to uppercase or rounding a number.

Date and Time Functions

Date and time functions in SQL are used to manipulate and extract information from date and time values. Common date and time functions include GETDATE, DATEADD, DATEDIFF, and DATEPART.

Example: To find the difference in days between two dates in an "Events" table, you would use the following SQL command:

        SELECT DATEDIFF(day, StartDate, EndDate) AS DaysDifference
        FROM Events;
    

Analogy: Think of date and time functions as tools that help you manage and calculate time-related data, like finding the duration between two events or extracting the year from a date.

Conclusion

Understanding SQL functions is crucial for performing various operations on data. Aggregate functions help summarize data, scalar functions transform individual values, and date and time functions manage time-related data. Mastering these functions allows you to manipulate and analyze data more effectively.