# Top 5 SQL Analytic Functions Every Data Analyst Needs to Know

SQL analytical functions to take your analysis skills to the next level. Analytical functions are one of the most popular tools among BI/Data analysts for performing complex data analysis.

Analytical functions are one of the most popular tools among BI/Data analysts for performing complex data analysis. These functions perform computations over multiple rows and return the multiple rows as well. Today we’ll cover 5 functions I find most useful, with a lot of practical examples.

For the uninitiated, the relative size of a query with an analytical function might seem a bit intimidating. Don’t worry, we have you covered. Most of these functions follow a basic syntax:

``````analytic_function_name([argument_list])
OVER (
[PARTITION BY partition_expression,…]
[ORDER BY sort_expression, … [ASC|DESC]])``````

There are three parts to this syntax, namely functionpartition by and order by. Let’s briefly cover what each one does:

• `analytic_function_name`: name of the function — like `RANK()``SUM()``FIRST()`, etc
• `partition_expression`: column/expression on the basis of which the partition or window frames have to be created
• `sort_expression`: column/expression on the basis of which the rows in the partition will be sorted

Okay, we’ve covered the basics thus far. For the practical part we’re gonna use the Orders table stored inside the PostgreSQL database:

Let’s begin with the practical part now, shall we?

## AVG() and SUM()

We’ve all been using aggregate functions such as `SUM``AVG``MIN``MAX`, and `COUNT` in our `GROUP BY` clauses. But when these functions are used over an `ORDER BY` clause they can give us running sum, mean, total, etc.

The following example will make it a lot more clear — we want to calculate the running average revenue and total revenue for each agent in the third quarter:

SELECT ord_date, agent_code, AVG(ord_amount) OVER (

PARTITION BY agent_code

ORDER BY ord_date

) running_agent_avg_revenue,

SUM (ord_amount) OVER (

PARTITION BY agent_code

ORDER BY ord_date

) running_agent_total_revenue

FROM orders

WHERE ord_date BETWEEN ‘2008–07–01’ AND ‘2008–09–30’;

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