Data Model / Database Implementation Jeffery S. Horsburgh Hydroinformatics Fall 2015 This work was funded by National Science Foundation Grants EPS and EPS

Objectives Understand common relational database software packages, limitations and capabilities Where are relational databases commonly used? Why and when would you use relational databases? Introduce MySQL functionality Create a physical implementation of an Observations Data Model (ODM) database within a RDBMS

Where We are Going Last week: Data Model/Database design – How do you design a data model for implementation within a relational database management system This week: Database implementation – How do you physically implement a data model as a database and load data Next week: Using Structured Query Language (SQL) – Using code to slice and dice your data once you have it in a database A little later: Accessing databases from client software – Getting data from a database into Python

Steps in Data Model Design 1.Identify entities 2.Identify relationships among entities 3.Determine the cardinality and participation of relationships 4.Designate keys / identifiers for entities 5.List attributes of entities 6.Identify constraints and business rules 7.Map 1-6 to a physical implementation

Physical Data Model The “physical” means a specific implementation of the data model – Choice of hardware and operating system – Choice of relational database management system – Implementation of tables, relationships, constraints, triggers, indices, data types – Database access and security – Performance – Storage

Summary of 3 Levels of Data Model Design FeatureConceptualLogicalPhysical Entity NamesXX Entity RelationshipsXX AttributesX Primary KeysXX Foreign KeysXX Table NamesX Column NamesX Column Data TypesX ViewsX Stored ProceduresX TriggersX ConstraintsX

Robust software for managing data Data stored in tables that may be related Based on Structured Query Language (SQL) – Adopted by the American National Standards Institute (ANSI) and the International Standards Organization (ISO) as the standard data access language Relational Database Management Systems

Relational Database Management Systems (RDBMS) File vs. server based Free vs. commercial Different data types Potentially different syntax for SQL queries Security models and concurrent users

File Versus Server-Based RDBMS File-based – Everything contained within a single file – Generally good for single user, desktop applications – Examples: SQLite, Microsoft Access Server-based – A database “server” manages databases and all transactions – Good for multiple, simultaneous connections and transactions – Examples: Oracle, Microsoft SQL Server, MySQL, PostgreSQL

The Beauty of Server-Based RDBMS Database Database Server With RDBMS Authentication and Access Control Simultaneous Data Users I want some data! Do I recognize your IP address? Do I know you? Are you authorized? Data Firewall Yay!

Server-Based RDBMS – “Granules” Database Server Databases Tables Records DB1 SiteVariableDateValue 1Temperature8/2/ : Temperature8/2/ : Temperature8/2/ : Temperature8/2/ : DB3DB2DBn...

Who are the main contenders? Commercial software – Sybase Adaptive Server Enterprise – IBM DB2 – Oracle – Microsoft SQL Server – Teradata Free/GPL/Open Source: – MySQL – PostgreSQL

MySQL No limit on # of CPUs, fully featured, support for several OSs $0 without support, approx. $600-$6000 for subscription-based support Highly scalable, provides support for most types of indexes and storage methods

Things to Consider When Deciding on a RDBMS Price Operating System Support Most important features – ACID (Atomicity, Consistency, Isolation, Durability) – Referential Integrity support – Transactions support Scalability and security Availability of support and software Potential longevity

ACID Properties of Database Transactions Atomicity – each transaction is “all or nothing” Consistency – any transaction brings the database from one valid state to another Isolation – concurrent execution of transactions results in a system state that would be obtained if they executed serially Durability – once a transaction has been committed, it will remain so

Physical Implementation of a Data Model within a RDBMS 1.Create a new database 2.Create tables for entities 3.Define attributes and data types 4.Create relationships and define their properties 5.Define constraints All of this can be scripted/automated using SQL

MySQL Workbench MySQL Workbench is a powerful graphical DB management tool – Create and modify ER diagrams – Administrate databases (create, modify, backup / restore DB) – Create/ view / modify table data and other database objects – Write and execute SQL queries 17

Authentication in MySQL Performed when you connect to the database server Establishes your identity Enables you to create accounts for MySQL Server without giving access to the rest of the server “root” = system administrator access

Connecting to a MySQL Server Connecting to a MySQL Server requires: – The name of the server machine or IP address and port number (3306 is default) – Username – Password

DEMO: Connecting to a MySQL Server

Creating a New Database In MySQL Workbench, click the “Create new schema” button In MySQL, “Schema” = “Database”

Creating a New Database (2) In the "New schema" tab enter the name for your new schema, set the Default Collation, and click “Apply” Character Set: A set of symbols and encodings Collation: A set of rules for comparing characters in a set

DEMO: Creating and Deleting Databases in MySQL

Reduction of an ER Diagram to Tables Converting an ER diagram to table format is the basis for deriving a relational database – Entities are expressed as tables that contain data – A database is a collection of tables – Tables are assigned the same name as the entity – Each table has columns that correspond to attributes – each column has a unique name – Each column must have a single data type

Data Types Each attribute of an entity (column in a database table) must have a single data type Data types are enforced by RDBMS software Table: DataValues AttributeData TypeSample Data ValueIDInteger1 SiteIDInteger5 VariableIDInteger5 DateTimeDate/Time8/15/2013 4:30 PM DataValueDouble4.567

Data Types Data types can be specific to RDBMS software RDBMSIntegerFloating PointDecimalStringDate/Time MS SQL ServerTINYINT, SMALLINT, INT, BIGINT FLOAT, REALNUMERIC, DECIMAL, SMALLMONEY, MONEY CHAR, VARCHAR, TEXT, NCHAR, NVARCHAR, NTEXT DATE, DATETIMEOFFSET, DATETIME2, SMALLDATETIME, DATETIME, TIME MySQLTINYINT (8-bit), SMALLINT (16- bit), MEDIUMINT (24-bit), INT (32- bit), BIGINT (64- bit) FLOAT (32-bit), DOUBLE (aka REAL) (64-bit) DECIMALCHAR, BINARY, VARCHAR, VARBINARY, TEXT, TINYTEXT, MEDIUMTEXT, LONGTEXT DATETIME, DATE, TIMESTAMP, YEAR PostgreSQLSMALLINT (16- bit), INTEGER (32- bit), BIGINT (64- bit) REAL (32-bit), DOUBLE PRECISION (64-bit) DECIMAL, NUMERIC CHAR, VARCHAR, TEXT DATE, TIME (with/without TIMEZONE), TIMESTAMP (with/without TIMEZONE), INTERVAL Quick summary from:

Data Types in MySQL Numeric – Integer types: bit, tinyint, smallint, mediumint, int, bigint – Fixed-point types: decimal, numeric (exact numeric values to preserve precision) – Floating-point types: float, double (approximate values) Date and Time – date, datetime, timestamp, time, year Strings – char(size) – fixed length string, right padded – varchar(size) – variable length string – tinytext, text, mediumtext, longtext - text data block

Data Types in MySQL (2) Binary data – binary(size) – binary byte strings – varbinary(size) – tinyblob, blob, mediumblob, longblob – binary large object Spatial Data Types – geometry – point, multipoint – linestring, multilinestring – polygon, multipolygon

Data Types in MySQL (3) Nullable and NOT NULL types – All types in SQL Server may or may not allow NULL values Primary key columns – Define the primary key Auto-increment columns – Automatically increased values when a new row is inserted (auto-increment values) – Used in combination with primary key

Creating Tables Expand database view in the schemas list Right click on “Tables” and select “Create Table” 30

Creating Tables (2) Enter table name and define the table columns (name, data type, and properties): 31 Enter the name of the column here Choose the data type of the column here Choose properties here

Creating Tables (3) Defining column properties – PK – the column is the primary key for the table – NN – the column is not nullable – UQ – Unique Index, the values in the column must be unique – BIN – the values in the column are binary – UN – the values in the column are unsigned – ZF – Zero fill, integer values will be padded with leading zeros for display – AI – the values in the column should be set automatically using an auto-increment (cannot be assigned manually) 32

Creating Tables (4) It is best practice to set the name of the table at the time it is created 33 Enter the name of the table here

DEMO: Creating and Deleting Tables 34

Creating Relationships Alter child table to add foreign key attribute Alter child table to add foreign key relationship Create and name the relationship Choose the referenced parent table Match the primary and foreign key attributes Choose what to do on update and delete

DEMO: Creating Relationships 36

Authorization in MySQL Assigning specific permissions to specific users for specific database objects

DEMO: Creating Database Users and Assigning Permissions in MySQL

Summary Physical database implementation requires choices about hardware, software, security, data types, formats and storage, and other factors RDBMS provide the ability to implement a database in a multi-user, server environment MySQL Workbench provides tools for database creation, editing, and administration – including forward and reverse engineering

Naming Conventions Tables – Each word is capitalized (Pascal Case) – But wait - MySQL’s default settings are to lower case database and table names!!! – In English, plural – Examples: Sites, Variables, DataValues Columns – In English, singular – Each word is capitalized (Pascal Case) – Avoid reserved words and characters (e.g., key, int, date ) – Examples: SiteID, SiteCode, SiteName 40

Naming Conventions (2) Primary key – Use " ID " or name_of_the_table + " ID " – Example: in the Sites table the PK column should be be called ID or SiteID Foreign key – Use the name of the referenced table + " ID " – Example: in the DataValues table the foreign key column that references the Sites table should be named SiteID 41

Naming Conventions (3) Relationship names (constraints) – In English, Pascal Case – " fk_ " + ParentTable + " _ " + ChildTable – Example: fk_Sites_DataValues View names – " v_ " + " name " – Example: v_SitesWithData Stored procedures names – " sp_ " + " name " – Example: sp_UpdateSeriesCatalog() 42

Advanced Database Objects Views Stored procedures Triggers Constraints Implementation of these objects may depend on your choice of RDBMS software

Database Views A View is equivalent to a table, but is defined by a SQL query Used to present a set of desired information, independent of the underlying database structure Can be used to hide complexities of the underlying data model from the user – One way to address the cons of normalization

Stored Procedures A set of structured query language (SQL) statements that are stored and executed on the server Useful for repetitive tasks Encapsulate functionality and isolate users from data tables Can provide a security layer – software applications have no access to the database directly, but can execute stored procedures

Triggers Special kind of stored procedure Automatically executes on a table or view when an event occurs in the database Events include: CREATE, ALTER, INSERT, UPDATE, DELETE Mostly used to maintain the integrity of information in the database

Constraints Common way to enforce data integrity Examples: – Not NULL – value in a column must not be NULL – Unique – value(s) in specified column(s) must be unique for each row in a table – Primary Key – value(s) in the specified column(s) must be unique for each row in the table and not be NULL – Foreign Key – values(s) in the specified column(s) must reference an existing record in another table via its primary key – Check – an expression that validates data and must not be FALSE