SQL Concepts

SQL stands for Structured Query Language; it is developed for managing the data in Relational Database Management System. SQL is based on relational geometry and tuple relational calculus; it is a database language that is used for creating database, deletion fetching rows and changing the rows and etc. Sometimes it is pronounced as S-Q-L and See-Qwell.

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All the DBMS like Oracle, MySQL, Sybase, Informix and SQL Server use SQL as conventional database language. it is required to create new database, tables and views, to insert, change delete and retrieve the data from database.

SQL is used to carry out the operations on the information held in database such as upgrading information, deleting information, creating and changing tables, views etc.

SQL is not a database; it is just a query language. To execute SQL queries you need to install some database for example SQL Server, DB2, Oracle, MySQL, MongoDB, PostGre SQL etc.

SQL helps to query our database in number of ways using English-like statements and with SQL user can access details from relational database management system. SQL allows client to describe the details and determinate the information in database and performance it when needed. SQL also allows client to create & drop the details and table.

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DDL– DDL stands for Data Definition Language and used to define the database structure. DDL allows you to perform these tasks;

  • Create, Modify and drop schema objects
  • Grant and revoke rights and roles
  • Analyze information on a desk, catalog, or cluster
  • Establish audit options
  • Add feedback to the details dictionary

The CREATE, ALTER, and DROP instructions need unique access to the specified item. For example, an ALTER TABLE declaration is not able if another customer has an open transaction on the specified table.

The GRANT, REVOKE, ANALYZE, AUDIT, and COMMENT instructions don’t need unique access to the specified item. For example, you can analyze a table while other users are upgrading the table.

Oracle Data source implicitly commits the present transaction before and after every DDL declaration.

Many DDL claims may cause Oracle Data source to recompile or reauthorize schema objects. For details on how Oracle Data source recompiles and reauthorizes schema objects and the conditions under which a DDL declaration would cause.

The DDL statements are:

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DML- DML stands for Data Manipulation Language and used for managing data in schema objects. Data Manipulate Language access and function the data in existing schema objects and these statements don’t implicitly commits the present transaction.

The DML statements are;

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The SELECT declaration is a limited type of DML declaration in that it can only accessibility data in the database. It cannot function data in the database, although it can function on the utilized data before returning the outcomes of the query.

The CALL and EXPLAIN PLAN statements are reinforced in PL/SQL only when implemented dynamically. All other DML statements are completely reinforced in PL/SQL.

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