SQL is abbreviation for “Structured Query Language“. This Language is for the Communication with relational Database`s. For the editing (Write, Change, Delete) as well as the query (Read) of Data.

But what exactly is SQL now?

Even if SQL is the term for communication, we use the word SQL in a wide variety of circumstances.

  • SQL Server
  • SQL Database
  • SQL Tables
  • SQL Views
  • SQL Backup
  • SQL Query / Commands

The SQL Server is a Product(e.g Microsoft-SQL Server) that´s there for it manage and provide the SQL Database´s. Furthermore can every single product much more like e.g “task planner”.

The SQL Databases is a collection from SQL Tables. No data is stored or accumulated directly in the SQL databases. All Databases are in SQL is a relationale Database.

In the SQL Tables ultimately saved the data that we collect.

The SQL Views is a logish Relation. In the SQL Views define a query (Select). You can work with a SQL View as with a SQL Table

The SQL Backup is a Backup from the SQL Database over respective SQL Server. There are various backup methods such as full backup, differential backup (since the last full backup) and transaction log backup (since the last backup)

The SQL Queries / Commands is the real meaning behind SQL. The Communication via SQL with the databases takes place either with a DBMS (DataBase Management System) or a program with SQL connection. Even though SQL is a general language, you cannot necessarily communicate 100% with all systems in the same way. This comes because of the SQL dialect that every database system (different SQL Server) has.

The different SQL-Commands Category´s

In addition to the normal commands such as read (select), write (insert), edit (update) and delete (delete), there are also other commands and various things to do (e.g. create database, count all values ​​together). The commands are therefore basically divided into 3 categories.

  • DML Commands (Data Manipulation Language)
  • DDL Commands (Data Definition Language)
  • DCL Commands (Data Control Language)

The category DML contains the basis like reading, editing, writing and deleting, the category DDL is there for the schema of a database. The last category DCL is for granting rights or controlling transactions (one execution).

Example for DML

  • Select * From TestTable
  • Delete From TestTable
  • Insert Into TestTable (column1,column2) values (“value1″,”value2”)

Example for DML

  • Create Table …
  • Alter Table …
  • Drop Index…

Example for DML

  • Grant on to…
  • Revoke…

Created on 08.05.2020

D. Borowski

Author from Ahaus Germany


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