Introduction to the Standard Query Language (SQL) to access data in relational databases. More information can be found at https://www.spiraltrain.nl/course-sql-fundamentals/?lang=en

1. SQL Fundamentals

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Course Schedule
• SQL Intro
• SQL Select Queries
• SQL Data Definition
• SQL Functions
• SQL Data Manipulation
• SQL Joins
• What is SQL?
• History of SQL
• SQL Standard
• SQL Parts
• SQL Environment
• Database Creation
• DDL Create Table
• SQL Data Types
• SQL Language Elements
• DML Insert Into
• SQL Errors
• Select Query
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What is SQL?
• Abbreviation of Structured Query Language :
• Standard language to access relational database management systems (RDBMS)
• Actually three languages can be distinguished
• Declarative query language with procedural elements :
• Used to create database schemas and to insert, update, delete and query data
• Data Definition Language (DDL) :
• Language that defines database structure (relation schemas)
• This includes creating, altering, and dropping tables and establishing constraints
• Data Manipulation Language (DML) :
• Query language to create, read, update and delete tuples (CRUD operations)
• Data Control Language (DCL) :
• Used to controls a database includes administering privileges and committing data
• SQL language further deals with the following issues :
• Transaction control , integrity constraints, views, embedded SQL and dynamic SQL
3SQL Intro

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History of SQL
• SQL started with name SEQUEL in the 1970's :
• Abbreviation of structured english query language
• Developed by Raymond F. Boyce and Donald D. Chamberlin
• Access data stored in IBM's System R relational database
• In 1979 Oracle introduced first commercial version of SQL :
• Oracle V2 (Version2) for VAX computers.
• In 1986 SQL first became an ANSI standard :
• SQL-89 known as SQL 1 was rather incomplete
• SQL-92 is known as first solid standard known as SQL 2
• SQL-99 known as SQL 3 :
— Recursive queries, triggers, object-oriented features
• SQL-2003 :
— Window functions, XML-related features
• SQL-2006 offers XML Query Language (XQuery) support
• SQL-2011 has improved support for temporal databases
SQL Intro 4

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SQL Standard
• SQL is standard but is not completely portable among RDBMS :
• This is caused by ambiguities and vendor extensions
• Specific SQL implementation by database vendor is SQL dialect
• Vendors implement parts of the SQL standard, e.g. most implement SQL-92
• Vendors add their vendor-specific extensions
• Most vendors conform to a set of Core SQL features :
• Portability might still be limited due to missing or additional features
• Purpose of SQL-92 and SQL-99 Standards :
• Specify syntax/semantics for data definition and manipulation
• Define data structures
• Enable portability
• Specify minimal (level 1) and complete (level 2) standards
• Allow for later growth/enhancement to standard
5SQL Intro

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SQL Parts
6SQL Intro

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SQL Environment
• Catalog :
• A set of schemas that constitute the description of a database
• Schema :
• Structure containing descriptions of objects created by a user
• This includes base tables, views, constraints
SQL Intro 7

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Database Creation
• Creating of database differs for different relational databases :
• Often done through a GUI interface particular for a database
• According to the SQL standard :
• SQL environment contains one or more catalogues :
• Each catalogue manages various metadata :
• Set of schemas consisting of :
— Relations/tables
— Views
— Assertions
— Indexes
• Users and user groups
• Many database use client-server model :
• You must connect to a remote host on certain port, log in and manage database
• SQLite database does not use this model, databases are files
8SQL Intro
Demo01
Create Database

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DDL Create Table
• Relational databases contain data in tables :
• Uniquely identified by their names and are comprised of columns and rows
• Columns contain the column name, data type, and other attributes
• Rows contain the records or data for the columns
• Tables are created through CREATE TABLE statement of SQL DDL :
CREATE TABLE inventory (
StockNumber INTEGER PRIMARY KEY,
Descrip VARCHAR(50),
OnHandQuan INTEGER,
PackQty INTEGER,
PackCost FLOAT
);
• Typically columns are created of certain data type
9SQL Intro
Demo02
DDL Create Table

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SQL Data Types
• Columns in a table are of certain data type :
• Often used data types are character strings, numbers and date types
• Character String types :
• CHAR(n) – fixed-length character data, n characters long bytes
• VARCHAR(n) – variable length character data
• LONG – variable-length character data
• Numeric types :
• NUMBER(p,q) – general purpose numeric data type
• INTEGER(p) – signed integer, p digits wide
• INTEGER - signed integer
• FLOAT(p) – floating point in scientific notation with p binary digits precision
• FLOAT – floating point in scientific notation
• Date/time type :
• DATE – fixed-length date/time in dd-mm-yy form
10SQL Intro

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SQL Language Elements
• Clauses :
• Constituent components of statements and queries, in some cases optional
• Expressions :
• Can produce either scalar values, or tables consisting of columns and rows of data
• Predicates :
• Specify conditions that can be evaluated to true, false or unknown) values
• Used to limit the effects of statements and queries or to change program flow
• Queries :
• Retrieve the data based on specific criteria
• Statements :
• May have a persistent effect on schemata and data
• May control transactions, program flow, connections, sessions or diagnostics
• SQL statements also include the semicolon (";") statement terminator
• Insignificant whitespace is generally ignored :
• Makes it easier to format SQL code for readability
11SQL Intro

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DML Insert Into
• Database table is filled with SQL INSERT INTO statements :
INSERT INTO inventory(StockNumber,Descrip,OnHandQuan,PackQty,PackCost)
VALUES (51002,'AA Dry Cells 4 Pack',173,12,9.00);
INSERT INTO inventory(StockNumber,Descrip,OnHandQuan,PackQty,PackCost)
VALUES (51004,'AA Dry Cells 8 Pack',5,12,16.80);
INSERT INTO inventory(StockNumber,Descrip,OnHandQuan,PackQty,PackCost)
VALUES (43512,'10W-30 Motor Oil, Quart',36,12,18.20);
INSERT INTO inventory(StockNumber,Descrip,OnHandQuan,PackQty,PackCost)
VALUES (51013,'D Dry Cells 8 Pack',19,12,90.20);
INSERT INTO inventory(StockNumber,Descrip,OnHandQuan,PackQty,PackCost)
VALUES (23155,'Shovel Pointed Long Handle',1500,1,9.82);
INSERT INTO inventory(StockNumber,Descrip,OnHandQuan,PackQty,PackCost)
VALUES (51001,'AAA Dry Cells 4 Pack ',92,12,9.00);
INSERT INTO inventory(StockNumber,Descrip,OnHandQuan,PackQty,PackCost)
VALUES (43111,'White Gas Gallon Can',14,4,14.75);
• Values listed in INSERT INTO statement :
• Must be in the same order as appearing in CREATE TABLE
• Character strings are surrounded with quotes, number not
12SQL Intro
Demo03
DML Insert Values

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SQL Errors
• SQL State Error Codes are defined by ISO/ANSI SQL Standards :
• 5-character string consisting of 2-characters followed by 3-character subclass value
• "00" indicates success, "01" indicates a warning
• Other class values normally indicate an exception
• Example Error Code :
• SQL0208 - ORDER BY column not in result table
• Typical error is duplicate primary key error :
• Trying to insert row with key already present
13SQL Intro
Demo04
Duplicate Key Error

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Select Query
• SELECT clause is used to retrieve data from database tables :
SELECT StockNumber,Descrip,OnHandQuan,PackQty,PackCost from inventory
• SELECT is followed by column names separated by comma’s
• Alternatively wild cards may be used to retrieve all columns :
SELECT * FROM inventory;
• SELECT can be combined with clauses WHERE, ORDER_BY etc.
14SQL Intro
Demo05
Select Query

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Summary : SQL Intro
• SQL is a declarative language to access RDBM Systems :
• Used to create database schemas and to query insert, update and delete data
• SQL is standard but is not completely portable among RDBMS’s :
• This is caused by ambiguities and vendor extensions
• SQL consists of three parts :
• Data definition, data manipulation and data control language
• SQL consist of several language elements :
• Clauses, expressions, predicates, queries and statements
• SQL Environments have catalogues with schema’s and users :
• Each schema defines tables, relations, views, assertions and indexes
• SQL Standard defines SQL State Error Codes :
• 5-character string consisting of 2-characters followed by 3-character subclass value
• SQL Standard defines data types :
• Columns in tables are of a certain data type
SQL Intro 15
Exercise 1
SQL Intro