It is one of the greatest skills for the developers who have to deal with the data. Letting you interplay with databases, perform your calculations, manipulate the data-thus generating useful insights-it is essential to know at least a list of primary SQL functions. Knowledge of most straightforward work can save time and ease it for the developers. Now, here is the top 10 SQL functions a developer must learn, their use in practice, and other added insights.
1. COUNT()
Definition:
COUNT() Function This function returns a count of rows in a table or rows where specified conditions occur.
It is one of the most sought after summary functions. For instance, if you have an e-commerce website, you can count orders by using COUNT to see how many orders you have conducted or count the number of how many customers came from a particular city. You could even figure out if a table is empty, or if it is filling up in some way with the information by using COUNT.
COUNT WITH DISTINCTION
Use COUNT with DISTINCTION to count the unique numbers in any column, which in your case will be your unique customer numbers.
2. SUM()
A SUM() adds all the numerical information in a column.
If you need to calculate the total revenue from sales or the total cost of items purchased, SUM is the function to use. It’s often paired with GROUP BY clauses to break totals down by categories, such as monthly sales or product types.
Pro Tip:
Use conditions within a SUM, such as SUM(CASE WHEN status = ‘completed’ THEN amount ELSE 0 END), to calculate totals for specific criteria.
3. AVG()
Definition:
AVG() : returns average of a numeric column.
Advanced usage:
Use AVG in tracking trends: The average order value for your ecommerce site, and average time response for your ticket for the service desk. Very useful for taking a read over overall performance, plus where room exists for improvement might be seen from the statistics it gives out.
Pro tip.
Use AVG and also ROUND up so your output gets cleaned up on rounding decimal places
4. MAX() and MIN()
MAX returns the maximum value and MIN returns minimum value in the column. Detail discussion of follows:
These functions are purely critical when it comes to identifying the main metrics. For instance, you can use MAX to know what the highest sale amount has been on a given day, and you could use MIN to obtain the earliest date of registration for a given user. They help set boundaries, such as an amount of discount beyond which is not acceptable or minimum orders.
Add these functions with GROUP BY to find the maxima or minima of any category.
5. CONCAT()
It concatenates two or more strings into one string.
Use Case with Examples:
For example, if there are separate columns for a first name and a last name, CONCAT can merge two fields into one field called “Full Name.” And finally, it produces nice-looking output: when there is a need to obtain full addresses from the combination of a street field and a city/zip field.
Use CONCAT_WS (Concatenate With Separator) if you would be using any separator like comma or space in between the values.
6. NOW()
Explanation
NOW() returns the current date and time.
Use Case in Detail
NOW is mainly used to store timestamps whenever a transaction has been made, a user logged into an account, or updated a system. It will ensure that time-sensitive data like order timestamps or login times are recorded accordingly.
Pro Tip:
Match NOW with DATE_FORMAT to determine your output format style for the date and time.
7. ROUND()
Makes a number exact to a defined number of decimal places
The Example in Practice
Most work you do involving calculations needs reliable financial information. In reports, however, three decimal places can get pretty sloppy. ROUND allows you to look good and in presentable order, whether you use it as part of an equation solving a price or a tax level or an interest rate.
Tip Use ROUND with AVG to calculate a rounded average in your report for aesthetics.
8. UPPER() and LOWER()
Definition:
UPPER() converts text to uppercase, while LOWER() converts text to lowercase.
Advanced Example Use Case:
These functions are great for standardizing data, such as forcing email addresses to be stored in all lowercase to keep things consistent. They also come in handy when doing case-insensitive searches or comparisons.
Pro Tip:
You use these functions with LIKE for flexible text matching like WHERE LOWER(email) LIKE ‘%example.com’.
9. COALESCE()
COALESCE() returns the first nonnull value from a list of arguments.
Nulls can be pretty destructive in calculations or bad reports. Use COALESCE() to replace with default values when null occurs. For example, if no user has entered his phone number, COALESCE() may replace it by “N/A”.
Pro Tip:
Use COALESCE on SELECT statements to elide messy output or on JOIN conditions to have mismatched data work.
10. SUBSTRING()
SUBSTRING() takes out a specified length of characters from a text string.
Long Use Case for Substrings
This can be applied for substrings in text by extracting an area code from the phone number getting a product ID from text input, etc. It is really great for formatting and breaking down complex strings into usable manageable components.
Pro Tip
Using SUBSTRING with CHARINDEX to find the presence of specific characters in the string, then using those characters dynamically to extract a needed part from there.
Conclusion
These 10 SQL functions form the basis under which developers work providing more modes of data analysis, manipulation, and presentation. A full-fledged knowledge in these functions helps develop efficient queries along with streamlined workflow creation for applications to be the best.
