Creating Tables and Relationships
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Foreign(Key(Constraints(
Foreign(Key(Constraints( ! Foreign(key:(a(rule(that(a(value(appearing(in(one(rela3on(must( appear(in(the(key(component(of(another(rela3on.( – aka(values(for(certain(a9ributes(must("make(sense."( – Po9er(example:(Every(professor(who(is(listed(as(teaching(a(course(in(the( Courses(rela3on(must(have(an(entry(in(the(Profs(rela3on.( ! How(do(we(express(such(constraints(in(rela3onal(algebra?( ! Consider(the(rela3ons(Courses(crn,(year,(name,(proflast,(…)(and( Profs(last,(first).( ! We(want(to(require(that(every(nonLNULL(value(of(proflast(in( Courses(must(be(a(valid(professor(last(name(in(Profs.( ! RA((πProfLast(Courses)((((((((⊆ π"last(Profs)( 23( Foreign(Key(Constraints(in(SQL( ! We(want(to(require(that(every(nonLNULL(value(of(proflast(in( Courses(must(be(a(valid(professor(last(name(in(Profs.( ! In(Courses,(declare(proflast(to(be(a(foreign(key.( ! CREATE&TABLE&Courses&(& &&&proflast&VARCHAR(8)&REFERENCES&Profs(last),...);& ! CREATE&TABLE&Courses&(& &&&proflast&VARCHAR(8),&...,&& &&&FOREIGN&KEY&proflast&REFERENCES&Profs(last));& 24( Requirements(for(FOREIGN(KEYs( ! If(a(rela3on(R(declares(that(some(of(its(a9ributes(refer( to(foreign(keys(in(another(rela3on(S,(then(these( a9ributes(must(be(declared(UNIQUE(or(PRIMARY(KEY(in( S.( ! Values(of(the(foreign(key(in(R(must(appear(in(the( referenced(a9ributes(of(some(tuple(in(S.( 25( Enforcing(Referen>al(Integrity( ! Three(policies(for(maintaining(referen3al(integrity.( ! Default(policy:(reject(viola3ng(modifica3ons.( ! Cascade(policy:(mimic(changes(to(the(referenced( a9ributes(at(the(foreign(key.( ! SetLNULL(policy:(set(appropriate(a9ributes(to(NULL.( -
Referential Integrity in Sqlite
CS 564: Database Management Systems University of Wisconsin - Madison, Fall 2017 Referential Integrity in SQLite Declaring Referential Integrity (Foreign Key) Constraints Foreign key constraints are used to check referential integrity between tables in a database. Consider, for example, the following two tables: create table Residence ( nameVARCHARPRIMARY KEY, capacityINT ); create table Student ( idINTPRIMARY KEY, firstNameVARCHAR, lastNameVARCHAR, residenceVARCHAR ); We can enforce the constraint that a Student’s residence actually exists by making Student.residence a foreign key that refers to Residence.name. SQLite lets you specify this relationship in several different ways: create table Residence ( nameVARCHARPRIMARY KEY, capacityINT ); create table Student ( idINTPRIMARY KEY, firstNameVARCHAR, lastNameVARCHAR, residenceVARCHAR, FOREIGNKEY(residence) REFERENCES Residence(name) ); or create table Residence ( nameVARCHARPRIMARY KEY, capacityINT ); create table Student ( idINTPRIMARY KEY, firstNameVARCHAR, lastNameVARCHAR, residenceVARCHAR REFERENCES Residence(name) ); or create table Residence ( nameVARCHARPRIMARY KEY, 1 capacityINT ); create table Student ( idINTPRIMARY KEY, firstNameVARCHAR, lastNameVARCHAR, residenceVARCHAR REFERENCES Residence-- Implicitly references the primary key of the Residence table. ); All three forms are valid syntax for specifying the same constraint. Constraint Enforcement There are a number of important things about how referential integrity and foreign keys are handled in SQLite: • The attribute(s) referenced by a foreign key constraint (i.e. Residence.name in the example above) must be declared UNIQUE or as the PRIMARY KEY within their table, but this requirement is checked at run-time, not when constraints are declared. For example, if Residence.name had not been declared as the PRIMARY KEY of its table (or as UNIQUE), the FOREIGN KEY declarations above would still be permitted, but inserting into the Student table would always yield an error. -
Data Analysis Expressions (DAX) in Powerpivot for Excel 2010
Data Analysis Expressions (DAX) In PowerPivot for Excel 2010 A. Table of Contents B. Executive Summary ............................................................................................................................... 3 C. Background ........................................................................................................................................... 4 1. PowerPivot ...............................................................................................................................................4 2. PowerPivot for Excel ................................................................................................................................5 3. Samples – Contoso Database ...................................................................................................................8 D. Data Analysis Expressions (DAX) – The Basics ...................................................................................... 9 1. DAX Goals .................................................................................................................................................9 2. DAX Calculations - Calculated Columns and Measures ...........................................................................9 3. DAX Syntax ............................................................................................................................................ 13 4. DAX uses PowerPivot data types ......................................................................................................... -
The Unconstrained Primary Key
IBM Systems Lab Services and Training The Unconstrained Primary Key Dan Cruikshank www.ibm.com/systems/services/labservices © 2009 IBM Corporation In this presentation I build upon the concepts that were presented in my article “The Keys to the Kingdom”. I will discuss how primary and unique keys can be utilized for something other than just RI. In essence, it is about laying the foundation for data centric programming. I hope to convey that by establishing some basic rules the database developer can obtain reasonable performance. The title is an oxymoron, in essence a Primary Key is a constraint, but it is a constraint that gives the database developer more freedom to utilize an extremely powerful relational database management system, what we call DB2 for i. 1 IBM Systems Lab Services and Training Agenda Keys to the Kingdom Exploiting the Primary Key Pagination with ROW_NUMBER Column Ordering Summary 2 www.ibm.com/systems/services/labservices © 2009 IBM Corporation I will review the concepts I introduced in the article “The Keys to the Kingdom” published in the Centerfield. I think this was the inspiration for the picture. I offered a picture of me sitting on the throne, but that was rejected. I will follow this with a discussion on using the primary key as a means for creating peer or subset tables for the purpose of including or excluding rows in a result set. The ROW_NUMBER function is part of the OLAP support functions introduced in 5.4. Here I provide some examples of using ROW_NUMBER with the BETWEEN predicate in order paginate a result set. -
(BI) Using MS Excel Powerpivot
2018 ASCUE Proceedings Developing an Introductory Class in Business Intelligence (BI) Using MS Excel Powerpivot Dr. Sam Hijazi Trevor Curtis Texas Lutheran University 1000 West Court Street Seguin, Texas 78130 [email protected] Abstract Asking questions about your data is a constant application of all business organizations. To facilitate decision making and improve business performance, a business intelligence application must be an in- tegral part of everyday management practices. Microsoft Excel added PowerPivot and PowerPivot offi- cially to facilitate this process with minimum cost, knowing that many business people are already fa- miliar with MS Excel. This paper will design an introductory class to business intelligence (BI) using Excel PowerPivot. If an educator decides to adopt this paper for teaching an introductory BI class, students should have previ- ous familiarity with Excel’s functions and formulas. This paper will focus on four significant phases all students need to complete in a three-credit class. First, students must understand the process of achiev- ing small database normalization and how to bring these tables to Excel or develop them directly within Excel PowerPivot. This paper will walk the reader through these steps to complete the task of creating the normalization, along with the linking and bringing the tables and their relationships to excel. Sec- ond, an introduction to Data Analysis Expression (DAX) will be discussed. Introduction It is not that difficult to realize the increase in the amount of data we have generated in the recent memory of our existence as a human race. To realize that more than 90% of the world’s data has been amassed in the past two years alone (Vidas M.) is to realize the need to manage such volume. -
Keys Are, As Their Name Suggests, a Key Part of a Relational Database
The key is defined as the column or attribute of the database table. For example if a table has id, name and address as the column names then each one is known as the key for that table. We can also say that the table has 3 keys as id, name and address. The keys are also used to identify each record in the database table . Primary Key:- • Every database table should have one or more columns designated as the primary key . The value this key holds should be unique for each record in the database. For example, assume we have a table called Employees (SSN- social security No) that contains personnel information for every employee in our firm. We’ need to select an appropriate primary key that would uniquely identify each employee. Primary Key • The primary key must contain unique values, must never be null and uniquely identify each record in the table. • As an example, a student id might be a primary key in a student table, a department code in a table of all departments in an organisation. Unique Key • The UNIQUE constraint uniquely identifies each record in a database table. • Allows Null value. But only one Null value. • A table can have more than one UNIQUE Key Column[s] • A table can have multiple unique keys Differences between Primary Key and Unique Key: • Primary Key 1. A primary key cannot allow null (a primary key cannot be defined on columns that allow nulls). 2. Each table can have only one primary key. • Unique Key 1. A unique key can allow null (a unique key can be defined on columns that allow nulls.) 2. -
Rdbmss Why Use an RDBMS
RDBMSs • Relational Database Management Systems • A way of saving and accessing data on persistent (disk) storage. 51 - RDBMS CSC309 1 Why Use an RDBMS • Data Safety – data is immune to program crashes • Concurrent Access – atomic updates via transactions • Fault Tolerance – replicated dbs for instant failover on machine/disk crashes • Data Integrity – aids to keep data meaningful •Scalability – can handle small/large quantities of data in a uniform manner •Reporting – easy to write SQL programs to generate arbitrary reports 51 - RDBMS CSC309 2 1 Relational Model • First published by E.F. Codd in 1970 • A relational database consists of a collection of tables • A table consists of rows and columns • each row represents a record • each column represents an attribute of the records contained in the table 51 - RDBMS CSC309 3 RDBMS Technology • Client/Server Databases – Oracle, Sybase, MySQL, SQLServer • Personal Databases – Access • Embedded Databases –Pointbase 51 - RDBMS CSC309 4 2 Client/Server Databases client client client processes tcp/ip connections Server disk i/o server process 51 - RDBMS CSC309 5 Inside the Client Process client API application code tcp/ip db library connection to server 51 - RDBMS CSC309 6 3 Pointbase client API application code Pointbase lib. local file system 51 - RDBMS CSC309 7 Microsoft Access Access app Microsoft JET SQL DLL local file system 51 - RDBMS CSC309 8 4 APIs to RDBMSs • All are very similar • A collection of routines designed to – produce and send to the db engine an SQL statement • an original -
Pizza Parlor Point-Of-Sales System CMPS 342 Database
1 Pizza Parlor Point-Of-Sales System CMPS 342 Database Systems Chris Perry Ruben Castaneda 2 Table of Contents PHASE 1 1 Pizza Parlor: Point-Of-Sales Database........................................................................3 1.1 Description of Business......................................................................................3 1.2 Conceptual Database.........................................................................................4 2 Conceptual Database Design........................................................................................5 2.1 Entities................................................................................................................5 2.2 Relationships....................................................................................................13 2.3 Related Entities................................................................................................16 PHASE 2 3 ER-Model vs Relational Model..................................................................................17 3.1 Description.......................................................................................................17 3.2 Comparison......................................................................................................17 3.3 Conversion from E-R model to relational model.............................................17 3.4 Constraints........................................................................................................19 4 Relational Model..........................................................................................................19 -
Normalization Exercises
DATABASE DESIGN: NORMALIZATION NOTE & EXERCISES (Up to 3NF) Tables that contain redundant data can suffer from update anomalies, which can introduce inconsistencies into a database. The rules associated with the most commonly used normal forms, namely first (1NF), second (2NF), and third (3NF). The identification of various types of update anomalies such as insertion, deletion, and modification anomalies can be found when tables that break the rules of 1NF, 2NF, and 3NF and they are likely to contain redundant data and suffer from update anomalies. Normalization is a technique for producing a set of tables with desirable properties that support the requirements of a user or company. Major aim of relational database design is to group columns into tables to minimize data redundancy and reduce file storage space required by base tables. Take a look at the following example: StdSSN StdCity StdClass OfferNo OffTerm OffYear EnrGrade CourseNo CrsDesc S1 SEATTLE JUN O1 FALL 2006 3.5 C1 DB S1 SEATTLE JUN O2 FALL 2006 3.3 C2 VB S2 BOTHELL JUN O3 SPRING 2007 3.1 C3 OO S2 BOTHELL JUN O2 FALL 2006 3.4 C2 VB The insertion anomaly: Occurs when extra data beyond the desired data must be added to the database. For example, to insert a course (CourseNo), it is necessary to know a student (StdSSN) and offering (OfferNo) because the combination of StdSSN and OfferNo is the primary key. Remember that a row cannot exist with NULL values for part of its primary key. The update anomaly: Occurs when it is necessary to change multiple rows to modify ONLY a single fact. -
Data Definition Language
1 Structured Query Language SQL, or Structured Query Language is the most popular declarative language used to work with Relational Databases. Originally developed at IBM, it has been subsequently standard- ized by various standards bodies (ANSI, ISO), and extended by various corporations adding their own features (T-SQL, PL/SQL, etc.). There are two primary parts to SQL: The DDL and DML (& DCL). 2 DDL - Data Definition Language DDL is a standard subset of SQL that is used to define tables (database structure), and other metadata related things. The few basic commands include: CREATE DATABASE, CREATE TABLE, DROP TABLE, and ALTER TABLE. There are many other statements, but those are the ones most commonly used. 2.1 CREATE DATABASE Many database servers allow for the presence of many databases1. In order to create a database, a relatively standard command ‘CREATE DATABASE’ is used. The general format of the command is: CREATE DATABASE <database-name> ; The name can be pretty much anything; usually it shouldn’t have spaces (or those spaces have to be properly escaped). Some databases allow hyphens, and/or underscores in the name. The name is usually limited in size (some databases limit the name to 8 characters, others to 32—in other words, it depends on what database you use). 2.2 DROP DATABASE Just like there is a ‘create database’ there is also a ‘drop database’, which simply removes the database. Note that it doesn’t ask you for confirmation, and once you remove a database, it is gone forever2. DROP DATABASE <database-name> ; 2.3 CREATE TABLE Probably the most common DDL statement is ‘CREATE TABLE’. -
A Simple Database Supporting an Online Book Seller Tables About Books and Authors CREATE TABLE Book ( Isbn INTEGER, Title
1 A simple database supporting an online book seller Tables about Books and Authors CREATE TABLE Book ( Isbn INTEGER, Title CHAR[120] NOT NULL, Synopsis CHAR[500], ListPrice CURRENCY NOT NULL, AmazonPrice CURRENCY NOT NULL, SavingsInPrice CURRENCY NOT NULL, /* redundant AveShipLag INTEGER, AveCustRating REAL, SalesRank INTEGER, CoverArt FILE, Format CHAR[4] NOT NULL, CopiesInStock INTEGER, PublisherName CHAR[120] NOT NULL, /*Remove NOT NULL if you want 0 or 1 PublicationDate DATE NOT NULL, PublisherComment CHAR[500], PublicationCommentDate DATE, PRIMARY KEY (Isbn), FOREIGN KEY (PublisherName) REFERENCES Publisher, ON DELETE NO ACTION, ON UPDATE CASCADE, CHECK (Format = ‘hard’ OR Format = ‘soft’ OR Format = ‘audi’ OR Format = ‘cd’ OR Format = ‘digital’) /* alternatively, CHECK (Format IN (‘hard’, ‘soft’, ‘audi’, ‘cd’, ‘digital’)) CHECK (AmazonPrice + SavingsInPrice = ListPrice) ) CREATE TABLE Author ( AuthorName CHAR[120], AuthorBirthDate DATE, AuthorAddress ADDRESS, AuthorBiography FILE, PRIMARY KEY (AuthorName, AuthorBirthDate) ) CREATE TABLE WrittenBy (/*Books are written by authors Isbn INTEGER, AuthorName CHAR[120], AuthorBirthDate DATE, OrderOfAuthorship INTEGER NOT NULL, AuthorComment FILE, AuthorCommentDate DATE, PRIMARY KEY (Isbn, AuthorName, AuthorBirthDate), FOREIGN KEY (Isbn) REFERENCES Book, ON DELETE CASCADE, ON UPDATE CASCADE, FOREIGN KEY (AuthorName, AuthorBirthDate) REFERENCES Author, ON DELETE CASCADE, ON UPDATE CASCADE) 1 2 CREATE TABLE Publisher ( PublisherName CHAR[120], PublisherAddress ADDRESS, PRIMARY KEY (PublisherName) -
Microsoft Power BI DAX
Course Outline Microsoft Power BI DAX Duration: 1 day This course will cover the ability to use Data Analysis Expressions (DAX) language to perform powerful data manipulations within Power BI Desktop. On our Microsoft Power BI course, you will learn how easy is to import data into the Power BI Desktop and create powerful and dynamic visuals that bring your data to life. But what if you need to create your own calculated columns and measures; to have complete control over the calculations you need to perform on your data? DAX formulas provide this capability and many other important capabilities as well. Learning how to create effective DAX formulas will help you get the most out of your data. When you get the information you need, you can begin to solve real business problems that affect your bottom line. This is Business Intelligence, and DAX will help you get there. To get the most out of this course You should be a competent Microsoft Excel user. You don’t need any experience of using DAX but we recommend that you attend our 2-day Microsoft Power BI course prior to taking this course. What you will learn:- Importing Your Data and Creating the Data Model CALCULATE Function Overview of importing data into the Power BI Desktop Exploring the importance of the CALCULATE function. and creating the Data Model. Using complex filters within CALCULATE using FILTER. Using ALLSELECTED Function. Using DAX Syntax used by DAX. Time Intelligence Functions Understanding DAX Data Types. Why Time Intelligence Functions? Creating a Date Table. Creating Calculated Columns Finding Month to Date, Year To Date, Previous Month How to use DAX expressions in Calculated Columns.