SQL (Structured Query Language)

 
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DEFINE SQL?

SQL (pronounced "ess-que-el") stands for Structured Query Language. SQLis used to communicate with a database. SQL aimed to store, manipulate, and recover data stored in relational databases. This language allows us to pose complex questions of a database. It also provides a means of creating databases. SQL is very widely used. SQL is an ANSI (American National Standards Institute) standard computer language for accessing and manipulating database systems. Some common relational database management systems that use SQL are: Oracle, Sybase, Microsoft SQL Server, Access, Ingres, etc. Although most database systems use SQL, most of them also have their own additional proprietary extensions that are usually used on their system. The SQL that can be used on each one of the major RDBMS today is in different flavors. The SQL standard is fairly complex, and it is not practical to implement the entire standard. Each database vendor needs a way to differentiate its product from others. In this tutorial, such differences are noted where appropriate. There are many different versions of the SQL language, but to be in agreement with the ANSI standard, they must support the same major keywords in a similar manner (such as SELECT, UPDATE, DELETE, INSERT, WHERE, and others). "Update", "Delete", "Create", and "Drop" can be used to accomplish almost everything that one needs to do with a database.

Example of SQL Queries : -

Below is an example of a table called "Persons": -

Last Name First Name
Bhayani Deepali
Shah Pavan
Mehta Krutika

The table above contains three records and two columns (Last Name and First Name).


With SQL, we can query a database and have a result set returned.
A query like this : -

SELECT First Name FROM Persons

Gives a result set like this :-

First Name
Deepali
Pavan
Krutika

 
SELECT Statement
In a relational database, data is stored in tables. To Get data from table use SQL Select Statement.

 

DISTINCT
To Filter out duplicate values from a Column(s) in an table use SQL Distinct.

 

WHERE
To get conditional data from a table use SQL Where



AND OR
The AND- OR operator displays a row if ALL conditions listed are true.



LIKE
SQL Like is normally use to get similar string values from column(s) in an table.


IN
This feature is used in many ways to filter selective data In an column(s).

 

Not In
This feature is used in many ways to filter selective data Not In an column(s).


BETWEEN
SQL Between is use to get data from a column(s) between an given range.


HAVING

The SQL HAVING clause is used to restrict conditionally the output of a SQL.


GROUP BY

SQL GROUP BY Tutorial helps you to generate the summary output.

 

ORDER BY

The ORDER BY keyword is used to sort the result.


COUNT,SUM, AVG, MIN, MAX

They are the Aggregate functions as they summarize the result query.


ALIAS

SQL Alias is an element is used to replace a namespace in the style sheet to a different namespace in the output.



JOIN

A join is used to combine rows from the multiple tables.


OUTER JOIN

SQL Tutorial outer Join is used when a join query is "united" with the rows not included in the join, and are especially useful if constant text are included.

 

Subquery

Sub Queries are useful where the desired output is based on some query or when we do not have the predefined list of values.


UNION

SQL Tutorial union is used in occasions where you want to see the results of multiple queries together, combining their output.


INTERSECT

Intersect gives a single set of records which are common in both the queries.


MINUS

The MINUS query returns all rows in the first query that are not returned in the second query.

 

OTHER

The others contains defination of store procedures, its benefits and types of store procedures.


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