Structured
Query Language-TCCICOMPUTERCOACHING.COM
SQL is
a database computer language designed for the retrieval and management of data
in relational database. SQL stands for Structured Query Language.
SQL- Structured
Query Language is a special-purpose programming language designed for
managing data held in a relational database management system (RDBMS), or for
stream processing in a relational data stream management system (RDSMS).
SQL is
used to communicate with a database. According to ANSI (American National
Standards Institute), it is the standard language for relational database
management systems. SQL statements are used to perform tasks such as update
data on a database, or retrieve data from a database. Some common relational
database management systems that use SQL are: Oracle, Sybase, Microsoft SQL
Server, Access, Ingres, etc.
SQL was
one of the first commercial languages for Code’s relational model, as
described in his influential 1970 paper, "A Relational Model of Data for
Large Shared Data Banks.". Despite not entirely adhering to the relational model as described
by Codd, it became the most widely used database language
The
standard SQL commands such as "Select", "Insert",
"Update", "Delete", "Create", and
"Drop" can be used to accomplish almost everything that one needs to
do with a database. This tutorial will provide you with the instruction on the
basics of each of these commands as well as allow you to put them to practice
using the SQL Interpreter.
A
database most often contains one or more tables. Each table is identified by a
name (e.g. "Customers" or "Orders"). Tables contain records
(rows) with data.
In this
tutorial we will use the well-known North wind sample database (included in MS
Access and MS SQL Server).
For
example, to display data from database, select command is used,
SELECT * FROM Customers;
The
most common operation in SQL, the query, makes use of the
declarative SELECT statement. SELECT retrieves data from
one or more tables, or expressions. Standard SELECT statements have
no persistent effects on the database. Some non-standard implementations
of SELECT can have persistent effects, such as the SELECT
INTO syntax provided in some databases.
SQL
keywords are NOT case sensitive like any other c language: select is the same
as SELECT
Some of the Most Important SQL
Commands:
SELECT -
extracts data from a database
UPDATE -
updates data in a database
DELETE -
deletes data from a database
INSERT
INTO - inserts new data into a database
CREATE
DATABASE - creates a new database
ALTER
DATABASE - modifies a database
CREATE
TABLE - creates a new table
ALTER
TABLE - modifies a table
DROP
TABLE - deletes a table
CREATE
INDEX - creates an index (search key)
DROP
INDEX - deletes an index
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