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Aliases and Aggregates in SQL

If you work with relational databases, you should be familiar with Structured Query Language (SQL). SQL aliases and aggregates are a lifesaver when the data becomes too complex for simple SQL queries. In this post, we’ll talk about SQL aliases and look into how they can simplify difficult searches, improve readability, and provide us new insights into our data. After finishing this blog post, you’ll feel comfortable using SQL aliases in your SQL queries.

Introduction

The ability to give tables and their columns temporary names within a query is a basic part of the SQL language. When working with several tables or conducting computations, the SQL aliases are invaluable time-savers and make our queries more concise and easier to comprehend. When working with complex queries that involve several tables and columns with long names, it can be helpful to temporarily rename the table or column using an alias in SQL to make the query clearer and more concise. The “AS” keyword is used to specify aliases, albeit it is not required for table aliases.

The aliases can be used in several ways, some of the ways aliases can be used are:

  1. Table Aliases: To combine several tables together, it is helpful to be able to refer to individual tables by shorter, more descriptive names. The query can also be posed as:
SELECT o.order_id, c.customer_name
FROM orders AS o
JOIN customers AS c ON o.customer_id = c.customer_id;

  • Column Aliases: The column aliases provide a more descriptive name for columns in the result set or for renaming calculated values. The query for column aliases is:
SELECT first_name, last_name, salary * 12 AS annual_salary
FROM employees;

  • Aliases having aggregate functions: The aliases can also be used with aggregate functions for providing more meaningful names to the calculated values. The query for that is:
SELECT department_id, AVG(salary) AS avg_salary
FROM employees
GROUP BY department_id;

  • Subquery Aliases: Subqueries in SQL can also have aliases which makes it easier for us to refer to the subquery’s result within the main query and the query can be written as:
SELECT e.employee_id, e.first_name, s.max_salary
FROM employees AS e
JOIN (
                              SELECT department_id, MAX(salary) AS max_salary
                              FROM employees
                              GROUP BY department_id
) AS s ON e.department_id = s.department_id;

Let us now explore some of the scenarios where aliases shine brightly and are very useful:

  1. Readability in Joins: Aliases help in making JOIN operations between multiple tables more comprehensible. The example case that we can consider for this is the same one that we considered in the table aliases examples where instead of typing full names for ‘orders’ and ‘customers’ tables we used ‘o’ and ‘c’ respectively.
  2. Clarity with calculations: While performing calculations on columns, aliases can provide us with meaningful labels for the calculated values. We can easily transform and rename columns through aliases.
  3. Simplifying the subqueries: Subqueries in SQL can become unwieldy, however, aliases help us manage their results. Assigning an alias provides us clarity and distinction between main and subquery columns while we are using a subquery in a WHERE clause or joining the clause with a subquery.

Harnessing the power of Aggregates

Aggregates in SQL are functions for summarizing and analyzing data within a group and the aggregates work seamlessly with aliases for delivering insightful results. Some of the few ways of synergizing aggregates and aliases are:

  1. Meaningful aggregations: Aggregate functions such as SUM, AVG, MAX, and COUNT provide us valuable insights into the data, and pairing them with aliases helps us present results with more informative names.
  2. Grouping data with clarity: Aggregates often involve grouping data based on certain criteria and with aliases, we can label grouped columns and aggregates which makes it easier for us to understand the context of each result.

Real-world examples of SQL aliases

Some of the real-world examples for illustrating the power of SQL aliases and aggregates are:

  1. Analysis of data in Sales report: Using aliases, we can create a succinct query that will calculate total sales and average revenue per product category. The resulting table that we obtain will have meaningful column names and provides us with a clear snapshot of each category’s performance.
  2. Analysis of employee performance: Joining the employee data with aggregate performance metrics, aliases can present a comprehensive report.  

Conclusion

In this blog, we have extensively discussed SQL aliases and aggregates which are essential tools for simplification of complex queries and enhancing the readability of our SQL code as they help us to temporarily rename the table name or other names of the resulting set. With this, aliases present data in a more intuitive and informative manner which makes it easier for us to extract insights and make informed decisions. Aliases and aggregates help us deal with intricate joins, intricate calculations, or insightful aggregations. Mastering SQL aliases and utilizing them in our queries will unlock a new level of query elegance and data comprehension.

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