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SELECT *
FROM users;Notes
Good for quick exploration, but prefer explicit columns in production queries.
SQL Cheat Sheet
Core SQL syntax and patterns for querying, filtering, sorting, joining, grouping, and modifying data.
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SELECT Basics
Foundational read queries.
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SELECT id, email, created_at
FROM users;Notes
Selecting fewer columns often improves readability and can reduce I/O.
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SELECT DISTINCT country
FROM customers;Notes
DISTINCT applies to the full selected column combination.
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SELECT first_name AS given_name, last_name AS family_name
FROM users;Notes
Aliases are especially useful in reports and computed expressions.
Select literals and expressions
Project computed values directly in the result set.
sqlANYselectexpressions
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SELECT order_id, subtotal, tax, subtotal + tax AS total
FROM orders;Notes
Most SQL engines allow arithmetic, string, and function expressions in SELECT.
Filtering Rows
WHERE clause patterns.
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SELECT *
FROM users
WHERE status = 'active';Notes
Use WHERE to limit the result set before grouping or ordering.
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SELECT *
FROM invoices
WHERE amount > 1000
AND due_date < CURRENT_DATE;Notes
Combine predicates with AND and OR to express complex filters.
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SELECT *
FROM products
WHERE category IN ('books', 'games', 'toys');Notes
IN is often clearer than multiple OR comparisons.
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SELECT *
FROM events
WHERE created_at BETWEEN DATE "2025-01-01" AND DATE "2025-01-31";Notes
BETWEEN is inclusive on both ends in standard SQL.
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SELECT *
FROM customers
WHERE email LIKE '%@example.com';Notes
Use % for any-length wildcard and _ for a single character.
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SELECT *
FROM tasks
WHERE completed_at IS NULL;Notes
Use IS NULL or IS NOT NULL, not = NULL.
Sorting and Limiting
ORDER BY, LIMIT, FETCH, OFFSET patterns.
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SELECT id, created_at
FROM orders
ORDER BY created_at DESC, id ASC;Notes
ORDER BY is applied after filtering and grouping.
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SELECT *
FROM logs
ORDER BY created_at DESC
LIMIT 50;Notes
LIMIT is widely supported, though standard SQL also supports FETCH FIRST.
Paginate with LIMIT and OFFSET
Skip rows and return a page-sized result set.
sqlANYpaginationlimitoffset
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SELECT *
FROM posts
ORDER BY published_at DESC
LIMIT 20 OFFSET 40;Notes
Offset pagination is simple but can be slower for large offsets.
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SELECT *
FROM employees
ORDER BY salary DESC
FETCH FIRST 10 ROWS ONLY;Notes
Supported in many modern SQL engines and part of the SQL standard.
Joins
Combine rows from multiple tables.
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SELECT o.order_id, c.name
FROM orders o
JOIN customers c ON c.customer_id = o.customer_id;Notes
INNER JOIN returns only matched rows.
Left join
Keep all rows from the left table and match rows from the right table.
sqlANYjoinleft-join
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SELECT c.customer_id, o.order_id
FROM customers c
LEFT JOIN orders o ON o.customer_id = c.customer_id;Notes
Rows without a match on the right side get NULLs for right-side columns.
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SELECT e.employee_id, d.department_name
FROM employees e
RIGHT JOIN departments d ON d.department_id = e.department_id;Notes
Many teams prefer rewriting RIGHT JOIN as LEFT JOIN for consistency.
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SELECT a.id AS a_id, b.id AS b_id
FROM a
FULL OUTER JOIN b ON b.id = a.id;Notes
Useful for reconciliation queries.
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SELECT e.employee_id, e.name, m.name AS manager_name
FROM employees e
LEFT JOIN employees m ON m.employee_id = e.manager_id;Notes
Self joins are common in hierarchical or parent-child tables.
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SELECT c.color, s.size
FROM colors c
CROSS JOIN sizes s;Notes
Cross joins multiply rows, so use them deliberately.
Aggregation and Grouping
Summaries and grouped queries.
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SELECT COUNT(*) AS row_count
FROM users;Notes
COUNT(*) includes rows regardless of NULL values.
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SELECT status, COUNT(*) AS total
FROM orders
GROUP BY status;Notes
All non-aggregated selected columns must appear in GROUP BY.
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SELECT country, status, COUNT(*) AS total
FROM customers
GROUP BY country, status;Notes
Useful for reports sliced by multiple categories.
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SELECT customer_id, COUNT(*) AS order_count
FROM orders
GROUP BY customer_id
HAVING COUNT(*) >= 5;Notes
WHERE filters rows before grouping; HAVING filters grouped results.
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SELECT
COUNT(*) AS total_rows,
SUM(amount) AS total_amount,
AVG(amount) AS avg_amount,
MIN(amount) AS min_amount,
MAX(amount) AS max_amount
FROM payments;Notes
Most SQL engines support these core aggregate functions.
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