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SQL AND OR

Compound conditions are made up of multiple simple conditions connected by AND or OR. There is no limit to the number of simple conditions that can be present in a single SQL statement.

The syntax for a compound condition is as follows:

SELECT "column_name"
FROM "table_name"

WHERE "simple condition"
{[AND|OR] "simple condition"}+

The {}+ means that the expression inside the bracket will occur one or more times. Note that AND and OR can be used interchangeably. In addition, we may use the parenthesis sign () to indicate the order of the condition.

For example, we may wish to select all stores with sales greater than $1,000 or all stores with sales less than $500 but greater than $275 in Table Store_Information,

Table Store_Information

store_name Sales Date
Los Angeles $1500 Jan-05-1999
San Diego $250 Jan-07-1999
San Francisco $300 Jan-08-1999
Boston $700 Jan-08-1999

we key in,

SELECT store_name
FROM Store_Information
WHERE Sales > 1000
OR (Sales < 500 AND Sales > 275)

Result:
store_name
Los Angeles
San Francisco

SQL Where

Next, we might want to conditionally select the data from a table. For example, we may want to only retrieve stores with sales above $1,000. To do this, we use the WHERE keyword. The syntax is as follows:

SELECT "column_name"
FROM "table_name"
WHERE "condition"

store_name Sales Date
Los Angeles $1500 Jan-05-1999
San Diego $250 Jan-07-1999
Los Angeles $300 Jan-08-1999
Boston $700 Jan-08-1999

we key in,

SELECT store_name
FROM Store_Information
WHERE Sales > 1000

Result:
store_name
Los Angeles

For More Details: http://www.1keydata.com/sql/sqlwhere.html

Select Distinct

The SELECT keyword allows us to grab all information from a column (or columns) on a table. This, of course, necessarily mean that there will be redundancies. What if we only want to select each DISTINCT element? This is easy to accomplish in SQL. All we need to do is to add DISTINCT after SELECT. The syntax is as follows:

SELECT DISTINCT "column_name"
FROM "table_name"

store_name Sales Date
Los Angeles $1500 Jan-05-1999
San Diego $250 Jan-07-1999
Los Angeles $300 Jan-08-1999
Boston $700 Jan-08-1999

we key in,

SELECT DISTINCT store_name FROM Store_Information

Result:
store_name
Los Angeles
San Diego
Boston

SQL Select

What do we use SQL commands for? A common use is to select data from the tables located in a database. Immediately, we see two keywords: we need to SELECT information FROM a table. (Note that a table is a container that resides in the database where the data is stored.

Table Store_Information
store_name Sales Date
Los Angeles $1500 Jan-05-1999
San Diego $250 Jan-07-1999
Los Angeles $300 Jan-08-1999
Boston $700 Jan-08-1999

SELECT store_name FROM Store_Information

Result:
store_name
Los Angeles
San Diego
Los Angeles
Boston

SQL Programming Help

This SQL programming help site lists commonly-used SQL statements, and is divided into the following sections:

* SQL Commands: Basic SQL statements for storing, retrieving, and manipulating data in a relational database.
* Table Manipulation: How SQL statements are used to manage tables inside the database.
* Advanced SQL: Advanced SQL commands.
* SQL Syntax: A single page that lists the syntax for all the SQL commands in this tutorial.

If you are interested in how to retrieve data using SQL, we recommend that you start with the SQL Commands section. If you are interested in understanding how SQL can be used to manipulate database tables, we recommend that you start with the Table Manipulation section. If you are looking for help on a specific SQL command, you can use the Site Map to find the command you are looking for.

For More Details
http://www.1keydata.com/sql/

What is SQL?

SQL (Structured Query Language) is a computer language aimed to store, manipulate, and retrieve data stored in relational databases. The first incarnation of SQL appeared in 1974, when a group in IBM developed the first prototype of a relational database. The first commercial relational database was released by Relational Software (later becoming Oracle).

Standards for SQL exist. However, the SQL that can be used on each one of the major RDBMS today is in different flavors. This is due to two reasons: 1) the SQL standard is fairly complex, and it is not practical to implement the entire standard, and 2) each database vendor needs a way to differentiate its product from others. In this tutorial, such differences are noted where appropriate.