Introduction to SQL
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This document introduces SQL and its basic concepts. It defines SQL as the language used to communicate with relational databases and retrieve data. It discusses that SQL can be pronounced as "S-Q-L" or "sequel" and describes how different vendors have extended SQL with their own commands while maintaining standard SQL. It outlines the different types of SQL statements and gives examples. It concludes by listing some common data types used in columns like integer, money, varchar, and date.
Introduction to SQL
- 1. Introduction to SQL Ram Kedem
- 2. Copyright 2014 © Ram Kedem. All rights reserved. Not to be reproduced without written consent Objectives • Defining SQL • Why do we need to use it ? • Pronouncing SQL: S-Q-L or Sequel? • Standard SQL and language adjustments • Types of SQL Statements • Basic column data types in MSSQL
- 3. Copyright 2014 © Ram Kedem. All rights reserved. Not to be reproduced without written consent Defining SQL • Structured Query Language • Allows users to communicate with Relational Databases and retrieve data from their tables. SQL RDBMS
- 4. Copyright 2014 © Ram Kedem. All rights reserved. Not to be reproduced without written consent Pronouncing : S-Q-L or Sequel? • SQL was developed at IBM and it was initially called “Structured English Query Language” (SEQUEL) and pronounced “sequel” • Later it was shortened to SQL - “Structured Query Language” • Both pronunciations are correct
- 5. Copyright 2014 © Ram Kedem. All rights reserved. Not to be reproduced without written consent Standard SQL and Language Extensions • The RDBMS model was implemented by many vendors – • Microsoft (SQL Server), Oracle, IBM (DB2), MySQL, Postgres, etc. • SQL is the language each of those vendors use in order to access and manipulate their databases • In most cases all vendors use the same SQL command in order to achieve the same goal. In some cases vendors will use specific SQL extention that will only work under their platform.
- 6. Copyright 2014 © Ram Kedem. All rights reserved. Not to be reproduced without written consent Standard SQL and Language Extensions • Same statement to retrieve data of one column • SELECT lastName FROM employees • Different statement to concatencate strings • SELECT 'hello' + 'world' (SQL Server) • SELECT 'hello' || 'world' (Oracle)
- 7. Copyright 2014 © Ram Kedem. All rights reserved. Not to be reproduced without written consent Types of SQL Statements • Data Manipulation Language (DML) statements are used for managing data within schema objects. For example : • SELECT - retrieve data from the a database • INSERT - insert data into a table • UPDATE - updates existing data within a table • DELETE – delete existing rows • Data Definition Language (DDL) statements are used to define the database structure or schema. For example : • CREATE - to create objects in the database • DROP - delete objects from the database • Data Control Language (DCL) statements. For example : • GRANT - gives user's access privileges to database • REVOKE - withdraw access privileges given with the GRANT command
- 8. Copyright 2014 © Ram Kedem. All rights reserved. Not to be reproduced without written consent Basic column data types • Numeric columns • INT - Integer (whole number) data value • Money - Numeric data types with fixed precision and scale Product id (int) Product price (numeric) Product name (varchar(25)) Experation (date) 1 53.3 Product1 2014/03/22 2 23.1 Product2 2014/02/21 3 32.3 Product3 2014/03/02
- 9. Copyright 2014 © Ram Kedem. All rights reserved. Not to be reproduced without written consent Basic column data types • Numeric columns • INT - Integer (whole number) data value • Money - Monetary or currency values String columns • VARCHAR(N) – String data • Date columns • DATE – date data Product id (int) Product price (money) Product name (varchar(25)) Experation (date) 1 53.3 Product1 2014/03/22 2 23.1 Product2 2014/02/21 3 32.3 Product3 2014/03/02
- 10. Copyright 2014 © Ram Kedem. All rights reserved. Not to be reproduced without written consent Essential Points • SQL is the language we use in order to communicate with the RDBMS • Although in most cases vendors use the same SQL command, in some cases the SQL command might be different • There are different categories to the SQL language, and each is responsible on different aspect • There are many different available data types is MSSQL Server, most basic columns are Int, Money, Varchar and Date.