Renaming Output with Aliases

Explanation

Sometimes a column's real name isn't the clearest label for your results, or a query gets hard to read once you're referencing several tables. An alias lets you give a column, or a table, a temporary name that only applies within that query.

Take the students table:

Running SELECT name FROM students gives you a column literally labeled name. If your result is going into a report alongside other kinds of names, SELECT name AS student_name FROM students makes the output much clearer without changing anything in the actual table.

Syntax

Aliasing a column:

SELECT column_name AS friendlier_name
FROM table_name;

Aliasing a table (useful once you start writing longer queries):

SELECT s.name
FROM students AS s;

AS is optional — column_name friendlier_name works too — but including it makes the intent obvious at a glance.

Interactive Example

Common Mistakes

• Trying to use a column alias inside the same query's WHERE clause. Most databases evaluate WHERE before the alias is assigned, so WHERE grade = 9 (using the real column name) is what you need, not WHERE grade_alias = 9.
• Forgetting quotes around an alias with spaces. If you want an alias containing a space, like "Student Name", it needs to be quoted; otherwise stick to a single word with no spaces.
• Confusing a table alias with renaming the table. FROM students AS s only creates a shorthand name for use within that query — the table is still called students everywhere else.

Best Practices

• Use column aliases to make ambiguous or cryptic column names readable in your results, especially for scores, counts, or calculated values.
• Use short table aliases (like s for students) once your queries start involving more than one table — it keeps things concise without hiding meaning.
• Keep alias names short but descriptive, and prefer AS explicitly even though it's optional, since it reads clearly to others.

Practice Question

Using the first playground above, write a query against the students table that returns the enrollment_year column aliased as year_joined, alongside the student's name.

Summary

Aliases, created with AS, let you rename columns and tables just for the scope of a query, without touching the underlying schema. They make results more readable and become especially useful once queries reference multiple tables.

FAQ