SQL Select Query

An SQL Select is used to Query a Database table or a combination of database tables.
A Basic structure of an SQL Select Query looks like the below.

SELECT [column1, column2,... columnN] FROM [tablename] WHERE 
		column1 (operation) value1 (condition) columnN (operation) valueN
		ORDER BY column1, columnN
		GROUP BY column1, columnN

Breaking down the above structure,
"SELECT column1, column2....columnN" - We are specifying a set of column names to be selected from the table.
FROM [tablename] - Here we are specifying the name of the table.
WHERE column1 (operation) value1 - The WHERE clause is optional. We are specifying filters on the TABLE.
Example: WHERE Customer_Name = "Jack Sparrow".
column1 refers to Customer_Name. operation refers to = and value1 refers to "Jack Sparrow".
condition is used to join two operations. Like AND or OR.
Example: WHERE Customer_Name = "Jack Sparrow" OR Customer_Name = "Third Street Saints"

Let us see an examples of SELECT Query which can make the above SYNTAX clear. Imagine we have a database TABLE called CUSTOMER.
If we want to query CUSTOMER to get all rows and columns, we can do that with a SELECT Query, as given below.

SELECT * FROM CUSTOMER

Result:

Rambo

Robert

Belgium

Mugambo

Satraj

Norway

Nagashekar

Rao

India

Tom

Harry

Brazil

Dana

Laura

Australia

Rambo

Fox

New Zealand

Giselle

Chivvi

Japan

In the above SELECT Query, we used *. * used in SELECT specifies to output all the columns from the table as a result.
What if we only wanted FIRSTNAME AND COUNTRY from the CUSTOMER TABLE? Then we can query the table as shown below.

SELECT FIRSTNAME, COUNTRY FROM CUSTOMER

Result:

Rambo

Belgium

Mugambo

Norway

Nagashekar

India

Tom

Brazil

Dana

Australia

Rambo

New Zealand

Giselle

Japan

If we want to get all records from Customer table sorted by Age in descending order, we can use ORDER BY Clause on the select query for the above scenario.

SELECT * from Customer ORDER BY AGE DESC

Result:

Giselle

Chivvi

Japan

Rambo

Fox

New Zealand

Nagashekar

Rao

India

Mugambo

Satraj

Norway

Tom

Harry

Brazil

Rambo

Robert

Belgium

Dana

Laura

Australia

In the above SELECT Query, we used ORDER BY statement to sort by AGE column in descending order. We can use ORDER BY columnname, if we want to sort in ascending order. By default, ORDER BY sorts by ascending order.