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SQL for beginners

Limiting results with LIMIT #

Sometimes a table has far more rows than you need. The LIMIT clause caps the number of rows a query returns:

SELECT
    column_name
FROM
    table
LIMIT
    number;
  • number: The maximum number of rows to return.

LIMIT is commonly combined with ORDER BY to answer questions like "who are the 3 oldest customers?":

SELECT
    first_name,
    last_name
FROM
    customers
ORDER BY
    age DESC
LIMIT
    3;

Without ORDER BY, LIMIT just returns however many rows the database happens to return first, which is not guaranteed to mean anything.

Exercise #

Write a command that retrieves the first_name and age columns from customers, sorted by age from oldest to youngest, and returns only the oldest 3 customers.

Tests #

  • The result has an age column.
  • The result contains exactly 3 rows.
  • The rows contain the 3 oldest customers, sorted from oldest to youngest.
Solution 
SELECT
    first_name,
    age
FROM
    customers
ORDER BY
    age DESC
LIMIT
    3;
Output will be displayed here