Task 2 – SQL Syntax
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Mayank Goyal
Database TablesA database most often contains one or more tables. Each table is identified by a name (e.g. “Customers” or “Orders”). Tables contain records (rows) with data. 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).
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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 * FROM Customers;
Try it Yourself »
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Keep in Mind That…SQL keywords are NOT case sensitive: select is the same as SELECT
In this tutorial we will write all SQL keywords in upper-case.
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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.
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Some of The Most Important SQL CommandsSELECT– 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
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