In this tutorial we will use the well-known Northwind sample database (included in MS Access and MS SQL Server).Below is a selection from the "Customers" table:
The table above contains five records (one for each customer) and seven columns (CustomerID, CustomerName, ContactName, Address, City, PostalCode, and Country).
SQL StatementsMost of the actions you need to perform on a database are done with SQL statements.The following SQL statement selects all the records in the "Customers" table:Example
Code: Select all
SELECT * FROM Customers;
Keep in Mind That...
- SQL keywords are NOT case sensitive: select is the same as SELECT
Semicolon after SQL Statements?Some database systems require a semicolon at the end of each SQL statement.Semicolon is the standard way to separate each SQL statement in database systems that allow more than one SQL statement to be executed in the same call to the server.In this tutorial, we will use semicolon at the end of each SQL statement.
Some of The Most Important SQL Commands
- SELECT - extracts data from a database
- UPDATE - updates data in a database
- DELETE - deletes data from a database
- INSERT INTO - inserts new data into a database
- CREATE DATABASE - creates a new database
- ALTER DATABASE - modifies a database
- CREATE TABLE - creates a new table
- ALTER TABLE - modifies a table
- DROP TABLE - deletes a table
- CREATE INDEX - creates an index (search key)
- DROP INDEX - deletes an index