ORDER BY

Without an explicit sort, the order rows come back in is not guaranteed — most databases return them in whatever order happens to be convenient internally. ORDER BY lets you control the order of the result set precisely.

ASC and DESC

Ascending (default) and descending order

SQL

SELECT first_name, last_name, salary
FROM employees
ORDER BY salary ASC;   -- lowest to highest

SELECT first_name, last_name, salary
FROM employees
ORDER BY salary DESC;  -- highest to lowest

ASC is the default — if you omit both keywords, the database sorts ascending.

Sorting by multiple columns

Listing more than one column sorts by the first column, and only uses later columns to break ties within groups of equal values in the earlier ones. Each column can have its own direction:

Sort by department, then salary within each department

SQL

SELECT first_name, last_name, department, salary
FROM employees
ORDER BY department ASC, salary DESC;

This groups employees alphabetically by department, and within each department, lists the highest earners first.

Sorting by column position

Some databases allow sorting by the numeric position of a column in the SELECT list instead of its name:

Sorting by position (works, but fragile)

SQL

SELECT first_name, last_name, salary
FROM employees
ORDER BY 3 DESC;  -- sorts by the 3rd selected column: salary

Prefer column names over position numbers

Sorting by position is fragile — if someone later reorders, adds, or removes a column from the SELECT list, the query silently starts sorting by a different column with no error at all. Using explicit column names in ORDER BY makes the intent clear and immune to that kind of accidental breakage.

Where NULLs sort

NULL sort position varies by database

Different databases place NULL values differently by default when sorting: PostgreSQL and Oracle sort NULL as the largest possible value by default (so it appears last in ASC order, first in DESC), while MySQL and SQL Server treat NULL as the smallest value (first in ASC, last in DESC). Most databases that support it let you control this explicitly with NULLS FIRST or NULLS LAST.

Explicit NULL placement (PostgreSQL, Oracle)

SQL

SELECT first_name, phone_number
FROM customers
ORDER BY phone_number ASC NULLS LAST;

Sorting by an expression or alias

Because ORDER BY runs after SELECT in the logical execution order, it can freely reference a column alias defined in the SELECT list, or repeat an expression directly:

Sorting by an alias

SQL

SELECT product_name, price * quantity AS total
FROM order_items
ORDER BY total DESC;