book

Head First SQL

Name: Head First SQL
Author: Lynn Beighley
ISBN: 9781449360443

by Lynn Beighley

August 2007

Beginner to intermediate

608 pages

13h 12m

English

O'Reilly Media, Inc.

Read now

Unlock full access

Head First SQL
Dedication
A Note Regarding Supplemental Files
Advance Praise for Head First SQL
Praise for other Head First books
Praise for the Head First Approach
Author of Head First SQL
How to use this Book: Intro
Who is this book for?Who should probably back away from this book?We know what you’re thinking.And we know what your brain is thinking.Metacognition: thinking about thinkingHere’s what WE didHere’s what YOU can do to bend your brain into submissionRead meThe technical review teamAcknowledgments
1. Data and Tables: A place for everything
Defining your dataLook at your data in categoriesWhat’s in a database?Your database viewed through x-ray specs...Databases contain connected dataTake command!Setting the table: the CREATE TABLE statementCreating a more complicated tableLook how easy it is to write SQLCreate the my_contacts table, finallyYour table is readyTake a meeting with some data typesYour table, DESCribedYou can’t recreate an existing table or database!Out with the old table, in with the newTo add data to your table, you’ll use the INSERT statementCreate the INSERT statementVariations on an INSERT statementColumns without valuesPeek at your table with the SELECT statementControlling your inner NULLNOT NULL appears in DESCFill in the blanks with DEFAULTYour SQL Toolbox
2. The SELECT Statement: Gifted data retrieval
Date or no date?Making contactA better SELECTWhat the * is that?How to query your data typesMore punctuation problemsUnmatched single quotesSingle quotes are special charactersINSERT data with single quotes in itHandle quotes with a backslashHandle quotes with an extra single quoteSELECT specific dataThe old waySELECT specific columns to limit resultsSELECT specific columns for faster resultsDoughnut ask what your table can do for you...Ask what you can do for your doughnutCombining your queriesFinding numeric valuesOnce is enoughSmooth Comparison OperatorsFinding numeric data with Comparison OperatorsText data roping with Comparison OperatorsSelecting your ingredientsTo be OR not to beThe difference between AND and ORUse IS NULL to find NULLsMeanwhile, back at Greg’s place...Saving time with a single keyword: LIKEThe call of the Wild(card)That’s more LIKE itSelecting ranges using AND and comparison operatorsJust BETWEEN us... there’s a better wayAfter the dates, you are either IN...... or you are NOT INMore NOTYour SQL Toolbox

3. DELETE and UPDATE: A change will do you good
Clowns are scaryClown trackingHow our clown data gets enteredBonzo, we’ve got a problemGetting rid of a record with DELETEUsing our new DELETE statementDELETE rulesThe INSERT-DELETE two stepBe careful with your DELETEThe trouble with imprecise DELETEChange your data with UPDATEUPDATE rulesUPDATE is the new INSERT-DELETEUPDATE in actionUPDATE your pricesAll we need is one UPDATEYour SQL Toolbox
4. Smart Table Design: Why be normal?
Two fishy tablesA table is all about relationshipsAtomic data30 minutes or it’s freeLocation, location, locationAtomic data and your tablesReasons to be normalThe benefits of normal tablesClowns aren’t normalHalfway to 1NFPRIMARY KEY rulesGetting to NORMALFixing Greg’s tableThe CREATE TABLE we wroteShow me theTime-saving commandThe CREATE TABLE with a PRIMARY KEY1, 2, 3... auto incrementallyAdding a PRIMARY KEY to an existing tableALTER TABLE and add a PRIMARY KEYYour SQL Toolbox
5. Alter: Rewriting the Past
We need to make some changesTable alteringExtreme table makeoverRenaming the tableWe need to make some plansRetooling our columnsStructural changesALTER and CHANGEChange two columns with one SQL statementQuick! DROP that columnA closer look at the non-atomic location columnLook for patternsA few handy string functionsTo SELECT the last two charactersTo SELECT everything in front of the commaUse a current column to fill a new columnHow our UPDATE and SET combo worksYour SQL Toolbox
6. Advanced Select: Seeing your data with new eyes
Dataville Video is reorganizingProblems with our current tableMatching up existing dataPopulating the new columnThe order does matterUPDATE with a CASE expressionLooks like we have a problemTables can get messyWe need a way to organize the data we SELECTTry a little ORDER BYORDER a single columnORDER with two columnsORDER with multiple columnsAn orderly movie_tableand the ordered results from our query:Reverse the ORDER with DESCThe Girl Sprout® cookie sales leader problemSUM can add them for usSUM all of them at once with GROUP BYAVG with GROUP BYMIN and MAXCOUNT the daysSELECT DISTINCT valuesLIMIT the number of resultsLIMIT to just second placeYour SQL Toolbox
7. Multi-Table Database Design: Outgrowing your table
Finding Nigel a dateWhy change anything?The query worked really wellIt worked too wellIgnoring the problem isn’t the answerToo many bad matchesUse only the first interestA possible matchMis-matchedAdd more interest columnsStarting overAll is lost...... But waitThink outside of the single tableThe multi-table clown tracking databaseThe clown_tracking database schemaAn easier way to diagram your tablesHow to go from one table to twoLinking your tables in a diagramConnecting your tablesForeign key factsConstraining your foreign keyWhy bother with foreign keys?CREATE a table with a FOREIGN KEYRelationships between tablesPatterns of data: one-to-onePatterns of data: when to use one-to-one tablesWhen to use one-to-one tablesPatterns of data: one-to-manyPatterns of data: getting to many-to-manyPatterns of data: we need a junction tablePatterns of data: many-to-manyPatterns of data: fixing gregs_listNot in first normal formFinally in 1NFComposite keys use multiple columnsEven superheros can be dependentShorthand notationsSuperhero dependenciesPartial functional dependencyTransitive functional dependencySecond normal formWe might be 2NF already...Third normal form (at last)And so, Regis (and gregs_list) lived happily ever afterThe EndYour SQL Toolbox
8. Joins and Multi-Table Operations: Can’t we all just get along?
Still repeating ourselves, still repeating...Prepopulate your tablesWe got the “table ain’t easy to normalize” bluesThe special interests (column)Keeping interestedUPDATE all your interestsGetting all the interestsMany paths to one placeCREATE, SELECT and INSERT at (nearly) the same timeCREATE, SELECT and INSERT at the same timeWhat’s up with that AS?Column aliasesTable aliases, who needs ’em?Everything you wanted to know about inner joinsCartesian joinReleasing your inner joinThe inner join in action: the equijoinThe inner join in action: the non-equijoinThe last inner join: the natural joinJoined-up queries?Your SQL Toolbox
9. Subqueries: Queries within queries
Greg gets into the job recruiting businessGreg’s list gets more tablesGreg uses an inner joinBut he wants to try some other queriesSubqueriesWe combine the two into a query with a subquerySubquery rulesSubquery rulesA subquery construction walkthroughA subquery as a SELECT columnAnother example: Subquery with a natural joinA noncorrelated subqueryA noncorrelated subquery with multiple values: IN, NOT INCorrelated subqueriesA (useful) correlated subquery with NOT EXISTSEXISTS and NOT EXISTSGreg’s Recruiting Service is open for businessOn the way to the partyYour SQL Toolbox
10. Outer Joins, Self-Joins, and Unions: New maneuvers
Cleaning up old dataIt’s about left and rightHere’s a left outer joinThe results of the left outer joinOuter joins and multiple matchesThe right outer joinWhile you were outer joining...We could create a new tableHow the new table fits inA self-referencing foreign keyJoin the same table to itselfWe need a self-joinAnother way to get multi-table informationYou can use a UNIONUNION is limitedUNION rules in actionUNION ALLCreate a table from your unionINTERSECT and EXCEPTWe’re done with joins, time to move on to...Subqueries and joins comparedTurning a subquery into a joinA self-join as a subqueryGreg’s company is growingYour SQL Toolbox
11. Constraints, Views, and Transactions: Too many cooks spoil the database
Greg’s hired some helpJim’s first day: Inserting a new clientJim avoids a NULLFlash forward three monthsCHECK, please: Adding a CHECK CONSTRAINTCHECKing the genderFrank’s job gets tediousCreating a viewViewing your viewsWhat your view is actually doingWhat a view isInserting, updating, and deleting with viewsThe secret is to pretend a view is a real tableView with CHECK OPTIONYour view may be updatable if...When you’re finished with your viewWhen bad things happen to good databasesWhat happened inside the ATMMore trouble at the ATMIt’s not a dream, it’s a transactionThe classic ACID testSQL helps you manage your transactionsWhat should have happened inside the ATMHow to make transactions work with MySQLNow try it yourselfYour SQL Toolbox
12. Security: Protecting your assets
User problemsAvoiding errors in the clown tracking databaseProtect the root user accountAdd a new userDecide exactly what the user needsA simple GRANT statementGRANT variationsREVOKE privilegesREVOKING a used GRANT OPTIONREVOKING with precisionThe problem with shared accountsUsing your roleRole droppingUsing your role WITH ADMIN OPTIONREVOKE role with CASCADEREVOKE role with RESTRICTCombining CREATE USER and GRANTGreg’s List has gone global!Your SQL ToolboxHow about a Greg’s List in your city?Use SQL on your own projects, and you too could be like Greg!
A. Leftovers: The Top Ten Topics (we didn’t cover)
#1. Get a GUI for your RDBMSMySQL GUI toolsOther GUI tools#2. Reserved Words and Special CharactersSpecial CharactersReserved Words#3. ALL, ANY, and SOMEUsing ALLUsing ANYUsing SOME#4. More on Data TypesBOOLEANINTOther INT typesDATE and TIME types#5. Temporary tablesReasons you might want a temporary table:Create a temporary tableA temporary table shortcut#6. Cast your dataSome situations where you might want to use CAST()You can’t use CAST() in these situations#7. Who are you? What time is it?#8. Useful numeric functions#9. Indexing to speed things up#10. 2-minute PHP/MySQLA closer look at each line
B. MySQL Installation: Try it out for yourself
Get started, fast!Instructions and TroubleshootingSteps to Install MySQL on WindowsDownload your installerPick a destination folderClick “Install” and you’re done!Steps to Install MySQL on Mac OS X
C. Tools Roundup: All your new SQL tools
D.
SymbolsABCDEFGILMNOPSTUVW
Index
About the Author
Copyright

Content preview from Head First SQL

Chapter 8. Joins and Multi-Table Operations: Can’t we all just get along?

Welcome to a multi-table world. It’s great to have more than one table in your database, but you’ll need to learn some new tools and techniques to work with them. With multiple tables comes confusion, so you’ll need aliases to keep your tables straight. And joins help you connect your tables, so that you can get at all the data you’ve spread out. Get ready, it’s time to take control of your database again.

Still repeating ourselves, still repeating...

Greg noticed the same values for status, profession, interests, and seeking popping up again and again.

Prepopulate your tables

Wouldn’t it make sense to have a set list of values in some of the tables?

Having many duplicate values will make it easy to prepopulate the status, profession, interests, and seeking tables. Greg wants to load up those four tables with the values already in his old my_contacts table.

First he needs to query his table to find out what’s already in there. But he doesn’t want an enormous list of duplicate values.

Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.

Read now

Unlock full access

More than 5,000 organizations count on O’Reilly

O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.

Julian F.

Head of Cybersecurity

I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.

Addison B.

Field Engineer

I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.

Amir M.

Data Platform Tech Lead

I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.

Mark W.

Embedded Software Engineer

Publisher Resources

ISBN: 9780596526849Errata Page

Cloud Computing

Data Engineering

Data Science

AI & ML

Programming Languages

Software Architecture

IT/Ops

Security

Design