Term discuss various database

 

Web application database immense importance. Any good database applications easily. However, there are a lot database and relational databases are used normally. Some of the famous, such as Oracle Database (Oracle), (MySQL), PostgreSQL  (PgSQL) etc. Information stored in a database and query the data in accordance with (as needed) can be seen arranged.
Our SQL tutorial, how to query a database, it will be shown in different ways. Hundreds of functions, there are rules. Using the database query can be complex. Even if the result of the mathematical operation process can be seen in the data.
Generally, a web application that needs to be asked is this tutorial about that. Tutorials hope our SQL query will be able to better read and understand complex. These applications can be used to query all of our Advanced SQL section. Here’s how the database can be queried with SQL that will be discussed.
In fact, when you do a big project or a job that allows you to understand more when, how much is important to be able to query complex.
SQL = Structured Query Language relational database for managing a Languages ​​stronger. With the Language of any database system to manage data (Manipulate) and allows you to access, such as Oracle, MySQL, SQL Server, etc. It’s 4th generation language. However, it is not a complete programming language because it does not support data structures, such as loop, branch.
How to manage the SQL database in our blog we will discuss it ……
With What can be done?
To create a new database
To create a new table
Query can be
Data from the database can be brought up
The new record is inserted in the database
Records can be updated
Can be removed, etc.
For example, a statement
1.SELECT name, email FROM users WHERE salary> 40000;
The full statement is at the top of the query survival. Skywriter a database table, the column name back tick ( `), but the text does not work, then. I could write a query like the following as the top
SELECT`name`, `email` FROM`users` WHERE` salary`> 40000;
Most of the work done by the database statement following statement will select all records of the table with friends.
SELECT * FROM friends
But that is not case sensitive ‘select * from friends’ and ‘SELECT * FROM friends’ work and output both will be the same.
SQL DDL and DML
Who can be divided into two ways
DDL-Data Definition Language: It is made with the database, etc. is deleted. Index (keys) are defined, to create the connection between the two tables, the table was set constraints in the DDL statement is
CREATE DATABASE- to create a new database
ALTER DATABASE- database is performed
To create a new table CREATE TABLE-
ALTER TABLE- table is performed
CREATE INDEX- INDEX is made
DROP INDEX- INDEX are deleted
DML-Data Manipulation Language
Query (search) and update SQL is a part of the DML.
SELECT- brings up data from database
UPDATE- Data Update (Update), and
DELETE- delete data from database
Information database INSERT INTO