University:
Boston University
Course:
MET CS 201 | Introduction to Programming
Academic year:

2023
Views:

471

Pages:

56
Author:

Emery Coleman

Introduction to Databases Introduction • • • • What is Database Key Concepts Typical Applications and Demo Lastest Trends What is Database • Three levels to view: ▫ Level 1: literal meaning – the place where data is stored  Database = Data + Base, the actual storage of all the information that are interested ▫ Level 2: Database Management System (DBMS)  The software tool package that helps gatekeeper and manage data storage, access and maintenances. It can be either in personal usage scope (MS Access, SQLite) or enterprise level scope (Oracle, MySQL, MS SQL, etc). ▫ Level 3: Database Application  All the possible applications built upon the data stored in databases (web site, BI application, ERP etc). Examples at each level • Level 1: data collection  text files in certain format: such as many bioinformatic databases  the actual data files of databases that stored through certain DBMS, i.e. MySQL, SQL server, Oracle, Postgresql, etc. • Level 2: Database Management (DBMS)  SQL Server, Oracle, MySQL, SQLite, MS Access, etc. • Level 3: Database Application  Web/Mobile/Desktop standalone application - e-commerce, online banking, online registration, etc. Examples at each level • Level 1: data collection  text files in certain format: such as many bioinformatic databases  the actual data files of databases that stored through certain DBMS, i.e. MySQL, SQL server, Oracle, Postgresql, etc. • Level 2: Database Management System (DBMS)  SQL Server, Oracle, MySQL, SQLite, MS Access, etc. • Level 3: Database Application  Web/Mobile/Desktop standalone application - e-commerce, online banking, online registration, Wikipedia, etc. Database Types • Flat Model • Navigational databases ▫ Hierarchical (tree) database model ▫ Network/Graph model • • • • • Relational Model Object model Document model Entity–attribute–value model Star schema Typical Database Application Architecture app DBMS DB Data File Structure • Demo : ▫ Take a look at the following file directories:  MySQL -- C:\ProgramData\MySQL\MySQL Server 8.0\Data\  Access -- C:\ARCS_dbtutorial\db\access\  Postgresql -- /project/scv/examples/db/tutorial/data/postgresql/testdb/ Data File Structure - MySQL Data File Structure - Access Data File Structure - PostgreSQL ATTENTION !!! NO database files can be accessed directly, but only through the database engine, called “DBMS” Typical Database Application Architecture app DBMS DB Three Common Acronyms • SQL – Structured Query Language • CRUD – Create, Read, Update, Delete • ACID – Atomicity, Concurrency, Integrity and Durability (transaction) Disadvantage of conventional flat file ▫ Redundancy - same data may store in many different copies ▫ Inconsistency – data regarding to same business entity may appear in different forms, for example, state name, phone number, etc. This made it hard to modify data and keep clean track of change; even loss of data ▫ Mixture of all data together – not clear in logical relationships between the data columns, thus hard to understand and manage once the data structure gets complex ▫ Hard to maintain and manage ▫ No concurrency support (only one can operate on the file) First Acronym - ACID Atomicity – transactions are either all or none (commit/rollback) Consistency – only valid data is saved Isolation – transactions would not affect each other Durability – written data will not be lost Good example : bank transaction Most of challenges of ACID compliance come from multiple users/concurrent using of database How Databases solves the problem? • Self-describing data collection of related records (meta data, data about data) , detail explanation as below: - Self-describing means: ▫ Database not just contains data, but also contains definition of the structure of data, that can be considered ‘Meta data’; It includes many related info : table column definition, index and key info, constraints, etc ▫ At database application level, database can also store other application related meta data as well, it makes personalization and customization of the application according to user profile much easier to handle. The typical example could be the user preference for those common social media sites or e-commerce sites, etc. Database Content Typical Database • • • • User data Medadata Application metadata Index and other overhead • User Data: tables to store user data • Meta data: keep the structure (schema) of the data, including table name, column name and type and contraints over the column(s) • Application meta data: application specific meta data regarding to user settings or functions of the application • Index and other overhead data: used for improving performance and maintenance, such as logs, track, security, etc. Terminology and Concept – Tables (Relations) The very central concepts of relational databases are Tables (Relations), Relationships. Table (formally called ‘relation’) – is the building block of relational database. It stores data in 2D, with its row reflects one instance of record (tuple), and each of its column reflects one aspect of the attributes of all instances, column may also be called ‘field’. For example, A ‘student’ table may contains (student id, first name, last name, grade, school name, home address, …), and each row may represent one student’s information, and each column of the table represents one piece of information of all students. And this is called a ‘relation’. Primary Key and Foreign Key • Primary key: Unique Identifier made of one or more columns to uniquely identify rows in a table. If the primary key contains more than one column, it can be called ‘composite key’ as well. • Foreign Key: is the primary key of another table, which is referenced in the current table. It’s the key to establish the relationship between the two tables, and through DBMS, to impose referential integrity. Surrogate Key • Surrogate key is a unique column • added to a relation to use as the primary key when lack of natural column serves as primary key, or when composite key needs to be replaced for various reasons. • Surrogate key is usually in form of auto increment numeric value, and of no meaning to the user, and thus cd often hidden in the table, or form or other entity for the internal use. • Surrogate keys are often used in the place of composite key to add more flexibility to the table. Terminology and Concept – E-R model E-R Model: Entity-Relationship data model is the common technique used in database design. It captures the relationships between database tables and represent them in a graphical way. The relationships between two entities can be 1:1, 1:N, or M:N. And it is usually established through ‘foreign key’ constraint. Examples: 1:1 Employee – Locker 1:N Customer – Order, Order – Order Detail M:N Student – Course Sample E-R diagram #1 Sample E-R diagram #2 Sample E-R diagram #3 One more concept - Normalization Wikipedia definition: • Database normalization, or simply normalization, is the process of restructuring a relational database in accordance with a series of socalled normal forms in order to reduce data redundancy and improve data integrity. It was first proposed by Edgar F. Codd as an integral part of his relational model. • Normalization entails organizing the columns (attributes) and tables (relations) of a database to ensure that their dependencies are properly enforced by database integrity constraints. It is accomplished by applying some formal rules either by a process of synthesis (creating a new database design) or decomposition (improving an existing database design). Unnormalized Form (UNF) – same attributes can be contained in one row Example: Students take courses Id 1. Name Jack Courses Mathematics Chemistry 2. Tim Chemistry 3. Ana Physics Chemistry Id or Name Course1 Course2 1. Jack Mathematics Chemistry 2. Tim Chemistry 3. Ana Physics Chemistry First Normal Form (1NF) – each attributes can only have one single value in one row; no duplicated row; no row/column order Example: Students take courses Id Name Course 1. Jack Mathematics 4. Jack Chemistry 2. Tim Chemistry 3. Ana Physics 5. Ana Chemistry Second Normal Form (2NF) – 1NF + no partial dependency (non-key attributes may not depend on any of candidate keys) Example: Students take courses Id Name Course CourseID Department 1. Jack Mathematics M-1 Math 4. Jack Chemistry C-1 Chemistry 2. Tim Chemistry C-1 Chemistry 3. Ana Physics P-1 Physics 5. Ana Chemistry C-1 Chemistry Second Normal Form (2NF) – continue 1NF + no partial dependency (non-key attributes may depend on any of candidate keys) (Course) = Func(CourseID) Id Name CourseID 1. Jack 4. (Department) = Func(CourseID) M-1 Course Course ID Department Jack C-1 M-1 Mathematics Math 2. Tim C-1 C-1 Chemistry Chemistry 3. Ana P-1 P-1 Physics Physics 5. Ana C-1 Third Normal Form (3NF) – 2NF + no transitive dependency (non-key attributes may not depend on each other) Example: Students take courses Id Name Course CourseID Department Building_no building 1. Jack Mathematics M-1 Math 31 D 4. Jack Chemistry C-1 Chemistry 22 A 2. Tim Chemistry C-1 Chemistry 22 A 3. Ana Physics P-1 Physics 18 S 5. Ana Chemistry C-1 Chemistry 22 A Third Normal Form (3NF) – continue very similar to 2NF, but more strict; no functional dependency between non-key attributes at all. Id Name CourseID Building_no 1. Jack M-1 31 4. Jack C-1 22 2. Tim C-1 22 3. Ana P-1 18 5. Ana C-1 22 Course Course ID Department M-1 Mathematics Math C-1 Chemistry Chemistry P-1 Physics Physics Building_no Building 18 S 22 A 31 D Boyce–Codd Normal Form (BCNF) – 3NF + non dependency between all candidate keys Example: 3NF, but not BCNF - Today's Court Bookings Court Start Time End Time Rate Type 1 09:30 10:30 SAVER 1 11:00 12:00 SAVER 1 14:00 15:30 STANDARD 2 10:00 11:30 PREMIUM-B 2 11:30 13:30 PREMIUM-B 2 15:00 16:30 PREMIUM-A Boyce–Codd Normal Form (BCNF) – 3NF + non dependency between all candidate keys Example: convert to BCNF - Today's Court Bookings Today's Bookings Rate Type Rate Type Court Member Flag Member Flag Court Start Time End Time SAVER 1 Yes Yes 1 09:30 10:30 STANDARD 1 No Yes 1 11:00 12:00 PREMIUM-A 2 Yes No 1 14:00 15:30 PREMIUM-B 2 No No 2 10:00 11:30 No 2 11:30 13:30 Yes 2 15:00 16:30 One More Example – database anormalies My_Anomly_ex_bank_orig AccountNo Name Address AccountBal AccountRate 100001 Lee, Yuan 11 Main Street 23994.58 4.50 100002 Lee, Yuan 11 Main Street 100.74 0.00 100002 Tian, Fu 12 Main Street 100.74 0.00 100003 Wang, Michele 12 Main Street 2500.8 0.00 100004 Dong, Yuan 14 Main Street 32003.98 4.50 100052 Yuan, Ben 16 Main Street 37.38 0.00 One More Example My_Anomly_ex_bank_orig AccountNo Name Address AccountBal AccountRate 100001 Lee, Yuan 11 Main Street 23994.58 4.50 100002 Lee, Yuan 11 Main Street 100.74 0.00 100002 Tian, Fu 12 Main Street 100.74 0.00 100003 Wang, Michele 12 Main Street 2500.8 0.00 100004 Dong, Yuan 14 Main Street 32003.98 4.50 100052 Yuan, Ben 16 Main Street 37.38 0.00 One More Example My_Anomly_ex_bank_orig AccountNo Name Address AccountBal AccountRate 100001 Lee, Yuan 11 Main Street 23994.58 4.50 100002 Lee, Yuan 11 Main Street 100.74 0.00 100002 Tian, Fu 12 Main Street 100.74 0.00 100003 Wang, Michele 12 Main Street 2500.8 0.00 100004 Dong, Yuan 14 Main Street 32003.98 4.50 100052 Yuan, Ben 16 Main Street 37.38 0.00 One More Example My_Anomly_ex_bank_orig AccountNo Name Address AccountBal AccountRate 100001 Lee, Yuan 11 Main Street 23994.58 4.50 100002 Lee, Yuan 11 Main Street 100.74 0.00 100002 Tian, Fu 12 Main Street 100.74 0.00 100003 Wang, Michele 12 Main Street 2500.8 0.00 100004 Dong, Yuan 14 Main Street 32003.98 4.50 100052 Yuan, Ben 16 Main Street 37.38 0.00 One More Example My_Anomly_ex_bank_orig AccountNo Name Address AccountBal AccountRate 100001 Lee, Yuan 11 Main Street 23994.58 4.50 100002 Lee, Yuan 11 Main Street 100.74 0.00 100002 Tian, Fu 12 Main Street 100.74 0.00 100003 Wang, Michele 12 Main Street 2500.8 0.00 100004 Dong, Yuan 14 Main Street 32003.98 4.50 100052 Yuan, Ben 16 Main Street 37.38 0.00 Gu, Zhen (???) Advantages of Normalization BCNF+ normalization can eliminate all anomalies : ▫ No Redundancy ▫ No Inconsistency – all changes can only be made at the same place and keep consistent (because of the key constraints), in DB terminology – get away with all update anormaly. ▫ Normalization is the process of decomposition, so all the business concepts can be modeled with clear logical relationships ▫ The entire database system remains consistent over time as the database grows with least redundancy and much durability. ▫ Strong support to be ACID compliant Advantages of Normalization • No(less) data redundancy – means easy management, less storage, etc. • No headache caused by data operation anomalies. Good for data integrity and consistency. Disadvantages of Normalization • Take effort • May increase complexity in data structure • Data retrieving efficiency may be discounted due to the need of join of multiple tables; So may not be proper in read-intensive data applications • Sometimes the constraints may be too strict to be flexible to make some customized change needed. Disadvantages of Normalization • Hard to deal with complex data structures such as class, objects, rows in a field. • Query for comprehensive information can be costly.[6] • Due to fixed predesigned structure, it is not flexible in terms of restructure of data Modern applications • Today companies like Google, Amazon and Facebook deal with loads of data and storing that data in an efficient manner is always a big task. They use NoSQL database which is based on the principles of unnormalized relational model to deal with storage issue.Some of the examples of NoSQL databases are MongoDB, Apache Cassandra and Redis. These databases are more scalable and easy to query with as they do not involve expensive operations like JOIN. Denormalization • Normalization and denormalization both have advantages and disavantages. The best practice is always a trade off between the two. • Denormalization will increase the risk of loss of data integrity and the size of storage, but may gain the simplicity and intuitivity of presenting data. Denormalization - Example • Customer (CustomerID, Name, Address, Zip, City, State) Zip [PK] CustomerID [PK] CustomerID [PK] Name City Name Address State Address Zip [FK] Zip City State Denormalization - Example • This is the normalized table design CustomerID Name Address Zip 101 John 111 Main St 02132 102 Adam 17 Willow St 02451 103 Grace 333 Burke St 02132 Zip City State 02132 Boston MA 02451 Waltham MA Denormalization - Example • This is the denormalized table design CustomID Name Address Zip City State 101 John 111 Main St 02132 Boston MA 102 Adam 17 Willow St 02451 Waltham MA 103 Grace 333 Burke St 02132 Boston MA Database Operation/Administration • CRUD (Create/Read/Update/Delete) – four basic operations • All through SQL (Structured Query Language) ▫ ▫ ▫ ▫ ▫ ▫ Sublanguage DDL (Data definition Language) DQL (Data Query Language) DML (Data Manipulate Language) DCL (Data Control Language) Scope of SQL: Query (select), Manipulate(Insert/update/delete), Definition(Create/Modify tables/columns) , Access Control (permission) How to Learn SQL • Same approach as many other languages, get a language reference first ▫ https://www.w3schools.com/sql/sql_syntax.asp (Standard SQL, simple) ▫ https://docs.oracle.com/cd/B28359_01/server.111/b28286/expressions.ht m#SQLRF004 (complete, but more complicated, and may add its own flavor) • Start from basics (DDL, DML, DQL) • Extend to more complicate elements (Subquery/Join/Function/Store Procedure/Index/Programming) Demos and Exercises Microsoft Access Templates E-R schema in Microsoft Access Anomaly Data import/export via Microsoft Access (may do some real life demo using actual data file from audience) • Data import/export via MySQL • • • • Other Stuffs not covered by this tutorial • Database Administration: concurrency, security, backup, recovery, and many more • Database Performance tuning: indexing, server configurations • Database programming • Database Technology Trend: BigData challenge, Data Warehouse, BI system, NoSQL, Cloud, Hadoop/Spark, etc. BI Systems • • • • Reporting System Data Mining (Has big overlap with today’s ML/AI trend) Data Warehouse/Data Mart ETL (Extract/Transform/Load) Big Data • 4Vs: ▫ ▫ ▫ ▫ Volume – how big in storage is need? Variety – how diverse is the data ? Veracity – can data be verified/trusted? Velocity – how fast is the data being generated? Big Data Technologies • Predictive analytics: to discover, evaluate, optimize, and deploy predictive models by analyzing big data sources to improve business performance or mitigate risk. • NoSQL databases: key-value, document, and graph databases. • Search and knowledge discovery: tools and technologies to support self-service extraction of information and new insights from large repositories of unstructured and structured data that resides in multiple sources such as file systems, databases, streams, APIs, and other platforms and applications. • Stream analytics: software that can filter, aggregate, enrich, and analyze a high throughput of data from multiple disparate live data sources and in any data format. • In-memory data fabric: provides low-latency access and processing of large quantities of data by distributing data across the dynamic random access memory (DRAM), Flash, or SSD of a distributed computer system. • Distributed file stores: a computer network where data is stored on more than one node, often in a replicated fashion, for redundancy and performance. • Data virtualization: a technology that delivers information from various data sources, including big data sources such as Hadoop and distributed data stores in real-time and near-real time. • Data integration: tools for data orchestration across solutions such as Amazon Elastic MapReduce (EMR), Apache Hive, Apache Pig, Apache Spark, MapReduce, Couchbase, Hadoop, and MongoDB. • Data preparation: software that eases the burden of sourcing, shaping, cleansing, and sharing diverse and messy data sets to accelerate data’s usefulness for analytics. • Data quality: products that conduct data cleansing and enrichment on large, high-velocity data sets, using parallel operations on distributed data stores and databases. Summary of Training • List important points from each lesson. • Provide resources for more information on subject. ▫ List resources on this slide. ▫ Provide handouts with additional resource material.