2. SQL syntax

SQL Syntax rules

• SQL statements always start with a keyword.
• The SQL statement ends with a semicolon.
• SQL is case insensitive, meaning update is the same as update

Database tables

A database typically contains one or more tables. Each table is identified by a name (for example, "Customers" or "Orders"). The table contains records with data (rows).
In this tutorial, we will use the famous Northwind sample database (including MSAccess and MSSQLServer).

The following is the data selected from the "Customers" table:

City

CustomerID	CustomerName	ContactName	Address		PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. De la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbk?p	Christina Berglund	Berguvsv?gen 8	Lule?	S-958 22	Sweden

The table above contains five records (one for each customer) and seven columns (CustomerID, CustomerName, ContactName, Address, City, PostalCode, and country).

SQL statements

Most of the operations you need to perform on the database are done using SQL statements.

The following SQL statement selects all records in the "Customers" table:

Instance select * from Customers;

In this tutorial, we'll explain a variety of different SQL statements to you.

Please remember ...

• SQL is not case sensitive: Select is the same as select.
• In this tutorial, we will write all the SQL keywords in uppercase.

Semicolon after the SQL statement?

• Some database systems need to use semicolons at the end of each SQL statement.
• Semicolons are a standard way to separate each SQL statement in a database system so that you can execute multiple SQL statements in the same request to the server.
• In this tutorial, we will use semicolons at the end of each SQL statement.

Some of the most important SQL commands

• SELECT -Extract data from the database
• Update-Updates the data in the database
• Delete-deletes data from the database
• INSERT INTO-inserts new data into the database
• CREATE database-creating new databases
• alter database-Modify Databases
• CREATE TABLE-Creates a new table
• ALTER TABLE -Change (change) database table
• Drop Table-delete tables
• CREATE index-Creating indexes (search key)
• Drop Index-delete indexes

SELECT statement

Syntactic:

SELECT column_name(s) FROM table_name

SELECT statement and WHERE clause

Syntactic:

SELECT [*] FROM [TableName] WHERE [condition1]

Select statement with where and/or clauses

Syntactic:

SELECT [*] FROM [TableName] WHERE [condition1] [AND [OR]] [condition2]...

SELECT statement and ORDER BY

Syntactic:

SELECT column_name()FROM table_nameORDER BY column_name() ASC or DESC

INSERT into statement

Syntactic:

INSERT INTO table_name (column, column1, column2, column3, ...)VALUES (value, value1, value2, value3 ...)

UPDATE statement

Syntactic:

UPDATE table_nameSET column=value, column1=value1,...WHERE someColumn=someValue

Delete statement

Syntactic:

DELETE FROM tableNameWHERE someColumn = someValue

2. SQL syntax