Single-Table SELECT Statements
The following SQL statements use one table to retrieve, filter, sort, and count customer data.
SELECT * FROM Customers;SELECT CustomerID, CustomerName FROM Customers;SELECT CustomerName, Address, City, PostalCode FROM Customers WHERE Country = 'UK';SELECT ContactName, CustomerName FROM Customers ORDER BY ContactName;SELECT COUNT(*) FROM Customers;SELECT Country, COUNT(*) FROM Customers GROUP BY Country;SELECT Country, COUNT(*) FROM Customers GROUP BY Country ORDER BY COUNT(*) DESC, Country ASC;SELECT Country, COUNT(*) FROM Customers GROUP BY Country HAVING COUNT(*) > 10 ORDER BY COUNT(*) DESC, Country ASC;
Multiple-Table SELECT Statements
The following SQL statements use INNER JOIN to combine information from multiple related tables.
SELECT Customers.CustomerName, Orders.OrderID, Orders.OrderDate FROM Customers INNER JOIN Orders ON Customers.CustomerID = Orders.CustomerID;SELECT Customers.CustomerName, Orders.OrderID AS 'Order Number', Orders.OrderDate FROM Customers INNER JOIN Orders ON Customers.CustomerID = Orders.CustomerID;SELECT Customers.CustomerName, Orders.OrderID AS 'Order Number', Orders.OrderDate FROM Customers INNER JOIN Orders ON Customers.CustomerID = Orders.CustomerID ORDER BY Customers.CustomerName, Orders.OrderID;SELECT Orders.OrderID AS 'Order Number', Orders.OrderDate, Products.ProductName, OrderDetails.Quantity FROM Orders INNER JOIN OrderDetails ON Orders.OrderID = OrderDetails.OrderID INNER JOIN Products ON OrderDetails.ProductID = Products.ProductID;SELECT Orders.OrderID AS 'Order Number', Orders.OrderDate, Products.ProductName, OrderDetails.Quantity, OrderDetails.Quantity * Products.Price AS 'Extended Price' FROM Orders INNER JOIN OrderDetails ON Orders.OrderID = OrderDetails.OrderID INNER JOIN Products ON OrderDetails.ProductID = Products.ProductID;SELECT Orders.OrderID AS 'Order Number', Orders.OrderDate, Products.ProductName, OrderDetails.Quantity, OrderDetails.Quantity * Products.Price AS 'Extended Price' FROM Orders INNER JOIN OrderDetails ON Orders.OrderID = OrderDetails.OrderID INNER JOIN Products ON OrderDetails.ProductID = Products.ProductID WHERE Orders.CustomerID = 2;SELECT Orders.OrderID AS 'Order Number', Orders.OrderDate, Products.ProductName, OrderDetails.Quantity, OrderDetails.Quantity * Products.Price AS 'Extended Price' FROM Customers INNER JOIN Orders ON Customers.CustomerID = Orders.CustomerID INNER JOIN OrderDetails ON Orders.OrderID = OrderDetails.OrderID INNER JOIN Products ON OrderDetails.ProductID = Products.ProductID WHERE Customers.CustomerName = 'Around the Horn';
INSERT, UPDATE, and DELETE Statements
The following SQL statements add, change, and remove records in the database.
INSERT INTO Shippers (ShipperID, ShipperName, Phone) VALUES (4, 'On Time Delivery', '(503) 555 0123');UPDATE Products SET Price = Price + 1;UPDATE Products SET Price = Price - 1;UPDATE Shippers SET ShipperName = 'On-Time Delivery' WHERE ShipperID = 4;DELETE FROM Shippers WHERE ShipperID = 4;
What I Learned
While completing this activity, I learned how SQL can be used to work with information stored in a database. SELECT statements are useful because they allow users to retrieve specific records, filter results, sort data, count records, and group information in meaningful ways. I also learned how INNER JOIN statements connect related tables so that information from different parts of a database can be displayed together. INSERT, UPDATE, and DELETE statements are important because they allow users to add new records, change existing information, and remove data when needed. I can apply this knowledge in future web design, product design, and database-related projects because many websites and applications rely on organized information. Understanding SQL helps me better understand how data is stored, managed, and displayed behind the scenes.