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SQL Lesson 4: Filtering and sorting Query results

Introduction & Core Concept

By default, database tables do not guarantee any specific sorting order when returning rows. To organize records logically (e.g., alphabetical order, highest price first, most recent purchase date), we use the ORDER BY clause.

Following the column name, you specify either ASC (ascending order, from smallest to largest) or DESC (descending order, largest to smallest).

SELECT * FROM products ORDER BY price DESC;

To slice the top results and restrict the total number of rows returned, append LIMIT at the very end of your query.

SELECT * FROM products ORDER BY price DESC LIMIT 5;
💡 MSSQL Tip: If you are using Microsoft SQL Server, the LIMIT keyword does not exist! Instead, you would use TOP right after the SELECT keyword. For example: SELECT TOP 5 * FROM products ORDER BY price DESC;
Why & Where We Use It
  • Why We Use It: Slicing data with LIMIT prevents your screen from freezing when querying massive tables. Sorting with ORDER BY structures reports so stakeholders can spot trends instantly.
  • Where We Use It: Highlighting leaderboard ranks, displaying top 10 best-selling products, and pagination on website search pages.
    • Real-World Example

    The executive team wants to know the top 3 most expensive luxury items in the entire ShopMart inventory catalog. You sort by price descending and limit the output to exactly 3 rows.

    Best Practices: What to Do & What NOT to Do
  • What to Do: You can sort by multiple columns simultaneously! For example, ORDER BY category ASC, price DESC sorts items alphabetically by category first, and then sorts products within each category from most expensive to cheapest.
  • What NOT to Do: Never use LIMIT without an accompanying ORDER BY clause if you need consistent, reproducible results. If you omit ORDER BY, the database will return an arbitrary, unpredictable slice of rows!
    • Syntax & Pro Tips
    SELECT name, category, price 
FROM products 
ORDER BY price DESC 
LIMIT 3;
    Interactive Sandboxed Terminal (Preloaded DB Schema: SHOPMART)
    SQL Query WorkspaceSQLite v3.45 (WASM Mode)
    QUICK INSERT:
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