TIPS & TRICKS/
SQL Cheat Sheet: 40 Queries With Examples/

SQL Cheat Sheet: 40 queries with examples, free printable PDF

TIPS & TRICKS/
SQL Cheat Sheet: 40 Queries With Examples/

Tips & Tricks

SQL Cheat Sheet: 40 Queries With Examples

Written by FutureSavvy Team

Updated 9 Oct 2026 · 1 min read

Every query below runs against the same four tables: Orders (OrderID, CustomerID, OrderDate, ShipDate, Amount, Region, Status), Customers (CustomerID, CustomerName, City), OrderLines (OrderID, ProductID, Qty, UnitPrice) and Products (ProductID, ProductName, Category). The syntax is SQL Server's, which is what our courses teach; the handful of functions that differ elsewhere are marked. Each one has a one-line note on what it does and the mistake people most often make with it.

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Selecting and filtering

SQL

SELECT OrderID, OrderDate, Amount
FROM Orders;

Name the columns you want. SELECT * is fine for a look; in anything saved it breaks the day someone adds a column.

SQL

SELECT TOP 10 OrderID, Amount
FROM Orders
ORDER BY Amount DESC;

The ten largest orders. TOP without ORDER BY returns an arbitrary ten. LIMIT 10 at the end in MySQL and Postgres.

SQL

SELECT DISTINCT Region
FROM Orders;

Each region once. DISTINCT applies to the whole row, not just the first column listed.

SQL

WHERE Region = 'North' AND Amount > 1000

Both conditions must hold. The moment you mix AND with OR, bracket the OR.

SQL

WHERE Region IN ('North', 'South', 'East')

Any of a list. Shorter and faster than a chain of ORs.

SQL

WHERE OrderDate >= '2026-01-01' AND OrderDate < '2026-04-01'

The safe date range. BETWEEN '2026-01-01' AND '2026-03-31' drops every order placed after midnight on 31 March when the column has a time.

SQL

WHERE CustomerName LIKE 'A%'

Starts with A. % is any run of characters, _ is exactly one. A leading % means a full scan of the table.

SQL

WHERE Status IS NULL

Missing values. NULL equals nothing, including NULL, so = NULL returns no rows. IS NOT NULL for the opposite.

SQL

ORDER BY Region, OrderDate DESC

Sort by region, then newest first within each region. Each column gets its own direction.

Aggregating

SQL

SELECT COUNT(*) FROM Orders;

Rows in the table. COUNT(Status) counts only rows where Status is not NULL, which is a different number.

SQL

SELECT Region, SUM(Amount) AS Total, AVG(Amount) AS Average
FROM Orders
GROUP BY Region;

One row per region. Every column in the SELECT that is not inside an aggregate must appear in the GROUP BY.

SQL

SELECT Region, SUM(Amount) AS Total
FROM Orders
GROUP BY Region
HAVING SUM(Amount) > 50000;

Filter the groups after summing. WHERE filters rows before the grouping; HAVING filters the totals after.

SQL

SELECT COUNT(DISTINCT CustomerID) AS Customers
FROM Orders;

How many different customers ordered, not how many orders.

SQL

SELECT YEAR(OrderDate) AS Yr, MONTH(OrderDate) AS Mth, SUM(Amount) AS Total
FROM Orders
GROUP BY YEAR(OrderDate), MONTH(OrderDate)
ORDER BY Yr, Mth;

Monthly totals. Group by the expressions, not the aliases: the GROUP BY runs before the aliases exist.

Joins

SQL

SELECT o.OrderID, c.CustomerName
FROM Orders o
INNER JOIN Customers c ON o.CustomerID = c.CustomerID;

Only orders that have a matching customer. Alias the tables and prefix every column; an unprefixed name that exists in both fails.

SQL

SELECT o.OrderID, c.CustomerName
FROM Orders o
LEFT JOIN Customers c ON o.CustomerID = c.CustomerID;

Every order, with the customer name where there is one and NULL where there is not. The left table is the one you keep whole.

SQL

SELECT c.CustomerID, c.CustomerName
FROM Customers c
LEFT JOIN Orders o ON o.CustomerID = c.CustomerID
WHERE o.OrderID IS NULL;

Customers who have never ordered. The IS NULL test on the right-hand key is what turns a left join into a not-in.

SQL

SELECT p.Category, SUM(l.Qty * l.UnitPrice) AS Revenue
FROM Orders o
JOIN OrderLines l ON l.OrderID = o.OrderID
JOIN Products p ON p.ProductID = l.ProductID
GROUP BY p.Category;

Three tables chained. Each ON links the new table to one already in the query. Multiply per line inside the SUM, never SUM(Qty) * SUM(UnitPrice).

Subqueries and CTEs

SQL

WHERE CustomerID IN (SELECT CustomerID FROM Customers WHERE City = 'Leeds')

Filter on a list built from another table. If the inner query can return NULL, use EXISTS instead.

SQL

SELECT c.CustomerName
FROM Customers c
WHERE EXISTS (SELECT 1 FROM Orders o WHERE o.CustomerID = c.CustomerID AND o.Amount > 5000);

Customers with at least one order over 5,000. EXISTS stops at the first match, so it is usually the fastest way to ask 'has any'.

SQL

WHERE Amount > (SELECT AVG(Amount) FROM Orders)

Above-average orders. The subquery must return exactly one value or the query errors.

SQL

WITH Monthly AS (
  SELECT YEAR(OrderDate) AS Yr, MONTH(OrderDate) AS Mth, SUM(Amount) AS Total
  FROM Orders GROUP BY YEAR(OrderDate), MONTH(OrderDate)
)
SELECT * FROM Monthly WHERE Total > 10000;

A common table expression: name a result, then query it. Reads top-down instead of inside-out, and runs no slower than the nested version.

Conditions, text and dates

SQL

CASE WHEN Amount >= 1000 THEN 'Large'
     WHEN Amount >= 100 THEN 'Medium'
     ELSE 'Small' END AS Band

The first matching WHEN wins, so order the tests from highest to lowest. Leave out ELSE and everything unmatched is NULL.

SQL

SUM(CASE WHEN Status = 'Cancelled' THEN 1 ELSE 0 END) AS Cancelled

A conditional count in the same pass as the other totals. No second query, no join.

SQL

COALESCE(Region, City, 'Unknown')

The first value in the list that is not NULL. ISNULL(Region, 'Unknown') is the SQL Server two-argument version; COALESCE is standard everywhere.

SQL

CAST(Amount AS DECIMAL(10, 2)) AS Amount2dp

Change a column's type. CONVERT(VARCHAR(10), OrderDate, 23) does the same with a style: 23 is yyyy-mm-dd, 103 is dd/mm/yyyy.

SQL

DATEDIFF(DAY, OrderDate, ShipDate) AS DaysToShip

Boundaries crossed, not elapsed time: 23:59 on Monday to 00:01 on Tuesday is 1 day. Order is start, then end.

SQL

WHERE OrderDate >= DATEADD(MONTH, -3, CAST(GETDATE() AS DATE))

The last three months. CAST to DATE drops the time so the range starts at midnight.

SQL

CONCAT(c.CustomerName, ' (', c.City, ')') AS Label

Build text. CONCAT treats NULL as empty; the + operator turns the whole result NULL if any part is.

SQL

LEN(TRIM(CustomerName)) AS NameLength

Character count after stripping spaces. LEN alone ignores trailing spaces; compare with DATALENGTH if you suspect them. Postgres uses LENGTH.

SQL

EOMONTH(OrderDate) AS MonthEnd

Last day of the order's month. Group by it for month-end reporting without a calendar table.

Window functions

SQL

ROW_NUMBER() OVER (PARTITION BY CustomerID ORDER BY OrderDate DESC) AS rn

Numbers each customer's orders, newest first. Put it in a CTE and keep rn = 1 for the latest order per customer: the question joins get wrong.

SQL

SUM(Amount) OVER (PARTITION BY Region ORDER BY OrderDate) AS RunningTotal

Cumulative total within each region, no self-join. Leave out PARTITION BY for one running total across everything.

SQL

LAG(Amount) OVER (PARTITION BY CustomerID ORDER BY OrderDate) AS PreviousAmount

The previous row's value, for change-on-last-time columns. LEAD looks forward. The first row gets NULL.

SQL

RANK() OVER (ORDER BY Amount DESC) AS AmountRank

Ties share a rank and the next rank is skipped (1, 1, 3). DENSE_RANK does not skip (1, 1, 2).

Combining and changing data

SQL

SELECT CustomerID, OrderDate FROM Orders
UNION ALL
SELECT CustomerID, OrderDate FROM ArchivedOrders;

Stack two results with matching columns. UNION on its own removes duplicates and sorts to do it; use ALL unless you need the dedupe.

SQL

UPDATE Orders
SET Status = 'Closed'
WHERE OrderID = 5012;

The WHERE is the whole statement. Without it every row changes, and outside a transaction there is no undo.

SQL

DELETE FROM Orders
WHERE Status = 'Test';

Same warning. Run SELECT COUNT(*) with the same WHERE first and check the number before you run the DELETE.

SQL

BEGIN TRAN;
UPDATE Orders SET Status = 'Closed' WHERE Region = 'North';
-- check the row count, then one of:
ROLLBACK;  -- or COMMIT;

Try a change and back it out. Nothing is permanent until COMMIT, and a forgotten open transaction locks the table for everyone else.

SQL

CREATE VIEW vMonthlySales AS
SELECT YEAR(OrderDate) AS Yr, MONTH(OrderDate) AS Mth, SUM(Amount) AS Total
FROM Orders GROUP BY YEAR(OrderDate), MONTH(OrderDate);

Save a query as something you can SELECT from. Reports point at the view and you change the logic in one place. A view has no ORDER BY of its own.

Which course covers these

Selecting, filtering, GROUP BY and the inner and left joins are SQL Introduction to Querying. SQL Fundamentals of Querying is the one-day version for people who need to read and write everyday queries fast. Subqueries, CTEs, window functions, UNION, transactions and views are SQL Advanced Querying.

SQL Introduction to Querying SQL Fundamentals of Querying SQL Advanced Querying

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