Data Modeling
AWS SQL and Scripting Training
Topics
• Getting Started with a Database Project (the Capstone)
• Data Modeling Concepts
• Steps for Creating an ERD
• Getting Started with a Database Project (the Capstone)
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Create Database
AWS SQL and Scripting Training
SQLite Create Database
• Recall that a database is a ‘container’ that holds related
database tables
• A database is managed/controlled by a DBMS
• SQLite is the database management system that we are using
• We need to create a database within SQLite for our Capstone
project
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SQLite Create Database
• Syntax in SQLite for creating a database is:
DatabaseName.db
At the SQLite prompt enter in:
test.db is the database name
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Database is created… or is it?
• Note: Even though we have provided a database name, SQLite
does not actually create the database.
• SQLite will defer creating the database until you actually create
something inside of it, such as a table or a view.
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Using the SQLite test.db
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Viewing the contents
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Note on .headers and .mode
• First: We’ll cover the formatting commands in a subsequent
section.
• Next: We’ll discuss the select statement in a subsequent
section too.
• But, the .headers and .mode commands are used to improve
the formatting of the output.
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Getting Database Schema Information
• There are several commands that we can use to obtain information about
the contents of your database.
• Later, we’ll add tables to our database (using DDL).
• Presently, we have one table created based on our prior “create table”
command.
• We can view the tables by entering in the following command (which will
show the schema that contains the ’test’ table)
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Each table has an index (a key) that can be viewed
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Viewing the schema (the DDL) for a database
• Recall that we (a) created the database and (b) added the test
table to the database (using DDL)
• We can review the contents of the database schema by
entering in the .schema followed by the database name.
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View the schema of the database
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SQLite Mater Table Schema items
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Example: Using all schema items to view the contents of
a database
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Assignment: Create SQLite database
• Open SQLite on your computer
• Replicate the commands in this section
• Verify results
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SQL Concepts
AWS SQL and Scripting Training
Video: SQL or SEQUEL?
18
Section Context
• DDL – Data Definition Language. << create tables (this section)
• DML – Data Manipulation Language << subsequent section on
querying the database
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DDL
AWS SQL and Scripting Training
Data Definition Language (DDL)
• We can either create DDL ‘by hand’ (text) or (for some ER
design tools, the DDL can be automatically created from the
design)
• Keep in mind that a complete Data Dictionary can serve as a
basis for creating tables in the database.
• There are other DDL commands that will assist you in not only
creating the tables, but altering (changing) the table structure.
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DDL Statements
• CREATE – is used to create the database or its objects (like
table, index, function, views, store procedure and triggers).
• DROP – is used to delete objects from the database.
• ALTER-is used to alter the structure of the database.
• TRUNCATE–is used to remove all records from a table,
including all spaces allocated for the records are removed.
• COMMENT –is used to add comments to the data dictionary.
• RENAME –is used to rename an object existing in the
database.
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Create tables in the database
• Page 47
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DML
AWS SQL and Scripting Training
A Query, a Statement, and a Clause
• A query is a request (a question) that returns information from
the database.
• An SQL statement is any valid piece of SQL code that is
executed by the SQL engine.
• A clause is a subsection of a query containing at least one
keyword and relevant information needed by the query (clause
is a portion of a query).
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The SELECT statement
• Words in ALL CAPS are
SQL keywords.
• A query can contain
multiple clauses, each
starting with a keyword.
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Recap of SQL concepts
• A table is a two-dimensional grid of rows and columns that contain
data.
• Logical and Physical database terms include:
• Table (physical) = Entity (logical)
• Field (physical) = Attribute (logical)
• A database record is a row in a table or multiple rows in a table (with
a unique primary key)
• Data can exist as a variety of different data types, such as strings of
text, numbers, or special characters.
• Metadata describes the nature and format of the data, including any
minimum/maximum character length or required numbers, letters, or
special characters.
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Recap of SQL concepts
• Relational databases can contain many tables.
• Each table in a relational database should have a primary key
that serves as a unique identifier for a row in a given table.
• A foreign key is any column in a table that exists as a primary
key in another table.
• The relationship between tables and their primary and foreign
keys is called a database schema.
• A database schema can be shown visually by an ERD (Entity
Relationship Diagram), which serves as a blueprint for a
database.
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Recap of SQL concepts
• There are a variety of relational database (RDBMS) products
including the Oracle database, Microsoft SQL Server, MySQL,
IBM DB2 and SQLite. While they may differ in their interface to
some degree, the fundamental SQL engine is essentially the
same (not including extensions).
• The SELECT keyword is the most common SQL command
used in SQL queries.
• SQL statements can contain multiple clauses that use different
SQL keywords.
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Most common tasks in SQL
• Create, retrieve, update and delete data based on the selection
criteria (C.R.U.D.)
• Organize data in the selected order
• Join data from multiple tables
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Database (db), SQL, and Schema
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Database (db), NoSQL, Document/Graph/Key Value
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Video Review Questions (NoSQL)
AWS SQL and Scripting Training
Video Review Questions
34
Types of SQL statements
• Data Definition Language (DDL) consists of SQL commands that
are used to define the database schema. It is used to create and
modify the structure of database objects. Some DDL commands
include CREATE, DROP, and COMMENT (GeeksforGeeks, 2019).
• Data Manipulation Language (DML) are SQL commands that deal
with data manipulation within the database. Examples of DML
commands are DELETE, UPDATE, and INSERT (Technopedia,
2014).
• Data Control Language (DCL) are SQL commands that deal with
rights and permissions of the database. DCL commands include
GRANT, which gives users access privileges, and REVOKE, which
eliminates a user’s privileges (GeeksforGeeks, 2019).
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Recap of SQL
Category
Description
Examples*
Data definition language (DDL) A series of commands used to
ALTER; COMMENT; CREATE;
change the way data is stored in the DROP; RENAME; TRUNCATE
database and/or alter its structure.
Data manipulation language
(DML)
A series of commands used to add INSERT; UPDATE; DELETE
and/or manipulate data within the
existing database schema.
Data control language (DCL)
Two commands used to allow or
GRANT; REVOKE
remove access and/or privileges to
the database
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View
• A VIEW is a virtual table displaying the results of an SQL
statement.
• This can contain data from more than one table and runs when
it’s accessed so the data that is displayed is current. It’s useful if
you want a user to be able to see only certain data without
having access to the entire database.
37
Jeopardy: Database
• How to Convert ER Diagram to Relational Database:
https://www.learndb.com/databases/how-to-convert-er-diagramto-relational-database
39
What does the
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counselor do?
What can the
school counselor
help with?
Who does the
school counselor
talk to?
Will I see
the school
counselor?
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References