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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":
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| 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.
|
| 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.
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| OTHER |
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The others contains defination of store procedures,
its benefits and types of store procedures.
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