introduction to SQL query language beginner.ppt

A little bit of about our group and me
 Research Computing services, visit http://rcs.bu.edu for more info
 Consulting
 Teaching
 Graphics
 Optimization
 Experience:
 Database programming
 Software development

Tutorial Outlines
 What is SQL
 SQL History
 Terminology By Examples
 SQL Syntax By Examples
 SQL Category
 Small yet worth noting
points
 Tutorial sample db overview
 Schema of the sample db
 Data of the sample db
 Hands on Tutorial Setup
SCC Research Data Metrics
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What is SQL ( ‘Structured Query Language’ )?
 SQL stands for ‘Structured Query Language’
 SQL is domain-specific language, NOT a general programming language
 SQL is specialized to handle ‘structured data’ that follows relational
model – data that incorporates relations among entities and variables.
 Used to interact with relational databases to manage data: create,
populate, modify, or destroy data. Also can manage data access

SQL is a standard language
 Nevertheless, SQL is a ‘language’. It has its language specification – a set
of language elements, rules and syntax
 Rigid and structural:
 Since the underlying data model is structural, SQL is very ‘structural’
too - requiring rigid predefined schema as compared with those of
‘noSQL’
 Syntax and grammar is also strict
 SQL specific features – triggers, stored procedures

History of SQL
 First developed in 1970s by two scientists at IBM following a theory of
‘relational algebra’ by Edgar F. Codd, who was also an IBM scientist.
 First commercial implementation of SQL-based RDMBS was Oracle’s V2.
 First adopted by ANSI in 1986, and ISO in 1987 as standard.
 The latest version of the SQL standard is from 2016. There have been
very many versions in between.
 Though standardized, this does not necessarily mean SQL code can be
migrated between different RDBMS seamlessly (Why?)

Terminology - Structure
 Database
 Table
 Column
 Row
 Relation
 Primary key
 Foreign key

Take sample_ecomm.db as an Example - schema

Terminology - SQL Language Elements
 Clause
 Statement
 Query
 Function
 Stored Procedure
 Predicate
 Expression
 Keyword
 Identifier

A SQL Example From Wikipedia
A chart showing several of the SQL language elements that compose a single statement
(source: https://wikimedia.org/api/rest_v1/media/math/render/svg/b83ad563285f7b0ebb325226d91f25ca0bffa7cd )

Our Own Query Example
SELECT FirstName, LastName -- SELECT clause
FROM Customer -- FROM clause
WHERE Id=1 – WHERE Clause
Clean way:
SELECT FirstName, LastName FROM Customer WHERE Id=1

Complete Query Statement Syntax – Order Matters !
Clause Priority Required?
SELECT <columns> 5. Mandatory 
FROM <table> 1. Mandatory 
WHERE <predicate on rows> 2. Optional 
GROUP BY <columns> 3. Optional 
HAVING <predicate on groups> 4. Optional, work with GROUP BY
ORDER BY <columns> 6. Optional 
OFFSET 7. Optional
FETCH FIRST 8. Optional

SQL Category
1. Data Query Language (DQL) - used to query data
2. Data Manipulation Language (DML) – used to create/modify/destroy data
3. Data Definition Language (DDL) – used to define database schema
4. Data Control Language (DCL) – used for security and access control

Most Important SQL Statements
 SELECT - extracts data from a database (DQL)
 UPDATE - updates data in a database (DML)
 DELETE - deletes data from a database (DML)
 INSERT - inserts new data into a database (DML)
 CREATE DATABASE - creates a new database (DDL)
 CREATE TABLE - creates a new table (DDL)
 DROP TABLE - deletes a table (DDL)
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Attention Please !
1. SQL keywords and table/column names are NOT case sensitive: ‘select’ and ‘SELECT’ are the
same
2. The values stored in a table can be case-sensitive – depending on configuration
3. Usually single quotes (‘’) or double quotes (“”) don’t matter, but could be configured otherwise
4. Semicolon ‘;’ is the standard way to separate SQL statements. It can be required in some
DBMS to end each statement with a ‘;’ even after a single statement
5. Comments can be used to make SQL more readable. Usually ‘--’ for single line comment, and
‘/*’ and ’*/’ for multiline comments. Add ‘--’ at the beginning to indicate a comment line
6. Standard is NOT STANDARD – none of SQL standard is fully implemented by all vendors. Pay
attention to the differences that each vendor’s implementation have from the SQL ‘standard’

In this Tutorial
 We will use all upper-case for all keywords
 We will use double quotes “” to indicate strings
 We will end each SQL statement with a ‘;’

Keywords Used in this Tutorial
 SELECT
 *
 FROM
 ORDER BY
 ASC
 DESC
 AND
 OR
 NOT
 WHERE
 LIMIT
 DISTINCT
 AS
 GROUP BY
 INNER JOIN
 ON
 !=
 INSERT
 UPDATE
 DELETE
 CREATE
 TABLE
 LIKE
 %
 INTO
 VALUES
 DROP

Functions Used in this Tutorial
 COUNT()
 MIN()
 MAX()
 AVG()
 SUM()
 REPLACE()

Hands On Demo
Basic SELECT + WHERE
Aggregation SELECT + GROUP BY
JOIN SELECT + JOIN
WRITE Queries INSERT/UPDATE/DELETE

Tutorial Tools and Files Overview
DB GUI : DBBrowser for SQLite
- sufficient yet simple/clean interface for demo purpose
- SQLite engine is already embedded in this tool
Sample DB: sample_ecomm.db
- a simple example e-commerce db. We will explore it a bit more …

sample_ecomm.db preview – Customer

sample_ecomm.db preview – Supplier

sample_ecomm.db preview – Product

sample_ecomm.db preview – OrderHead

sample_ecomm.db preview – OrderItem

Tutorial Setup
All the tutorial files can be accessed from:
http://www.bu.edu/tech/support/research/training-consulting/live-tutorials/
Tutorial Setup Instruction is at the following subdirectory:
Intro2SQLpresentationinstr_tutorialSetup_vdi.docx
Tutorial Software - using BU’s Common Lab Apps. It can be accessed at:
https://rdweb.wvd.microsoft.com/arm/webclient/index.html

Some Extra Info:
 The following is some extra information you may be
interested in:
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GUI tool is not the only way!
A GUI tool like DB Browser is not the only way to
access databases!
There could be many other ways! The following are
the two ways:

SQLite Programming Interface - Python

SQLite Programming Interface - R

Useful Resources:
 This tutorial materials:
http://www.bu.edu/tech/support/research/training-consulting/live-tutorials/
 W3Schools SQL tutorial: https://www.w3schools.com/sql/
 Khan Academy:
https://www.khanacademy.org/computing/computer-programming/sql
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introduction to SQL query language beginner.ppt

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