Database Tables and Data Types

Creating and Modifying Database Tables

• A database table represents a real-world entity, which is a thing or concept that we want to store data about.
• Entities have attributes, which are the data points we want to store about them.
• To create a database table, we need to:
  • Identify the entity and its attributes
  • Decide on the columns and their data types
  • Consider the size of each column

Data Types in MySQL

• MySQL provides various data types to store different types of data:
  • Text data types (e.g., Char, Varchar, Text) for storing text data
  • Numeric data types (e.g., Tinyint, Smallint, Mediumint, Int, Bigint) for storing whole numbers
  • Date and time data types (e.g., Date, Datetime, Time, Year) for storing dates and times

Text Data Types

• Char: stores up to 255 characters, used for fixed-length strings
• Varchar: stores up to 65,535 characters, used for variable-length strings
• Text: stores larger amounts of text data
• When choosing a text data type, consider the maximum length of the data and whether it needs to store non-English characters

Numeric Data Types

• Tinyint: stores whole numbers from -128 to 127 (signed) or 0 to 255 (unsigned)
• Smallint: stores whole numbers from -32,768 to 32,767 (signed) or 0 to 65,535 (unsigned)
• Mediumint: stores whole numbers from -8,388,608 to 8,388,607 (signed) or 0 to 16,777,215 (unsigned)
• Int: stores whole numbers from -2,147,483,648 to 2,147,483,647 (signed) or 0 to 4,294,967,295 (unsigned)
• Bigint: stores whole numbers from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 (signed) or 0 to 18,446,744,073,709,551,615 (unsigned)
• When choosing a numeric data type, consider whether negative numbers are needed and the maximum value required

Date and Time Data Types

• Date: stores dates in the format 'YYYY-MM-DD'
• Datetime: stores dates and times in the format 'YYYY-MM-DD HH:MM:SS'
• Time: stores times in the format 'HH:MM:SS'
• Year: stores years in the format 'YYYY'
• When choosing a date and time data type, consider the level of precision required

Creating a Table in MySQL

• The basic syntax for creating a table is: CREATE TABLE table_name (column1 data_type, column2 data_type, ...);
• Each column is defined with a name, data type, and size (if applicable)
• The NOT NULL constraint can be used to make a column mandatory
• A comma separates each column definition, except for the last one### Database Design
• A database table is designed to store information about books.
• The table has 7 columns:
  • title (varchar, 200 characters, not null)
  • author (varchar, 50 characters, not null)
  • publication_date (date, not null)
  • number_of_pages (int, unsigned, not null)
  • publisher (varchar, 200 characters, not null)
  • genre (varchar, 15 characters, null)
  • retail_price (double, not null)

MySQL Commands

• CREATE TABLE command is used to create a new table in a database.
• The command starts with CREATE TABLE followed by the table name and the column definitions in parentheses.
• Each column definition includes the column name, data type, and any constraints (e.g. not null, unsigned).
• The command ends with a semicolon.

Creating a Table

• The CREATE TABLE command is executed in MySQL Workbench to create a new table called "book" in the "instructor" database.
• The table structure is verified by using the DESCRIBE command, which shows the column names, data types, and constraints.
• The SHOW CREATE TABLE command is used to display the entire SQL command that created the table.

Inserting Data

• The INSERT INTO command is used to add new records to a table.
• The command starts with INSERT INTO followed by the table name and the column names in parentheses.
• The values to be inserted are listed in the VALUES clause, in the same order as the column names.
• Each value is separated by a comma, and text values are enclosed in single quotes.
• The command ends with a semicolon.

Common Mistakes

• Failing to match the column names and values in the INSERT INTO command.
• Not enclosing text values in single quotes.
• Not specifying values for mandatory columns.

Retrieving Data

• The SELECT command is used to retrieve data from a table.

• The command starts with SELECT followed by the column names to be retrieved.

• The FROM clause specifies the table name.

• The command ends with a semicolon.

• The result set is displayed in MySQL Workbench.### Creating a Database Table in MySQL

• To create a database table, you need to decide what data you want to store and what attributes the data will have.

• In this case, the entity is a book, and the attributes are title, author, publication date, pages, publisher, genre, and retail price.

Understanding Entity Attributes

• Attributes are the data items you want to store about the entity (e.g., title, author, price).
• You need to know the name of the attribute (e.g., title) and the data type (e.g., text, number, date).
• You also need to decide on the length of the attribute (e.g., how long the title can be).

Data Types in MySQL

• MySQL offers various data types, such as varchar, date, decimal, and double.
• Different database systems (e.g., Oracle) may have different data types.

Designing the Table

• Design a table with the entity name, MySQL data types, and length.
• This design is conceptual and independent of the database system.

Creating the Table

• Use MySQL Workbench to connect to the MySQL server and create the table using the CREATE TABLE command.
• Add data to the table using the INSERT INTO command.

Importance of Practice

• Understanding the concept is one thing, but doing it is a different thing.
• Practice creating tables and experimenting with different data types to learn more.

Creating and Modifying Database Tables

• A database table represents a real-world entity, with attributes that are the data points we want to store about it.
• To create a table, we need to identify the entity and its attributes, decide on the columns and their data types, and consider the size of each column.

Data Types in MySQL

• MySQL provides various data types to store different types of data, including:
  • Text data types (e.g., Char, Varchar, Text) for storing text data
  • Numeric data types (e.g., Tinyint, Smallint, Mediumint, Int, Bigint) for storing whole numbers
  • Date and time data types (e.g., Date, Datetime, Time, Year) for storing dates and times

Text Data Types

• Char: stores up to 255 characters, used for fixed-length strings
• Varchar: stores up to 65,535 characters, used for variable-length strings
• Text: stores larger amounts of text data
• When choosing a text data type, consider the maximum length of the data and whether it needs to store non-English characters

Numeric Data Types

• Tinyint: stores whole numbers from -128 to 127 (signed) or 0 to 255 (unsigned)
• Smallint: stores whole numbers from -32,768 to 32,767 (signed) or 0 to 65,535 (unsigned)
• Mediumint: stores whole numbers from -8,388,608 to 8,388,607 (signed) or 0 to 16,777,215 (unsigned)
• Int: stores whole numbers from -2,147,483,648 to 2,147,483,647 (signed) or 0 to 4,294,967,295 (unsigned)
• Bigint: stores whole numbers from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 (signed) or 0 to 18,446,744,073,709,551,615 (unsigned)
• When choosing a numeric data type, consider whether negative numbers are needed and the maximum value required

Date and Time Data Types

• Date: stores dates in the format 'YYYY-MM-DD'
• Datetime: stores dates and times in the format 'YYYY-MM-DD HH:MM:SS'
• Time: stores times in the format 'HH:MM:SS'
• Year: stores years in the format 'YYYY'
• When choosing a date and time data type, consider the level of precision required

Creating a Table in MySQL

• The basic syntax for creating a table is: CREATE TABLE table_name (column1 data_type, column2 data_type,...);
• Each column is defined with a name, data type, and size (if applicable)
• The NOT NULL constraint can be used to make a column mandatory

Database Design

• A database table is designed to store information about books, with 7 columns:
  • title (varchar, 200 characters, not null)
  • author (varchar, 50 characters, not null)
  • publication_date (date, not null)
  • number_of_pages (int, unsigned, not null)
  • publisher (varchar, 200 characters, not null)
  • genre (varchar, 15 characters, null)
  • retail_price (double, not null)

Creating a Table

• The CREATE TABLE command is used to create a new table in a database
• The command starts with CREATE TABLE followed by the table name and the column definitions in parentheses
• Each column definition includes the column name, data type, and any constraints (e.g., not null, unsigned)
• The command ends with a semicolon

Inserting Data

• The INSERT INTO command is used to add new records to a table
• The command starts with INSERT INTO followed by the table name and the column names in parentheses
• The values to be inserted are listed in the VALUES clause, in the same order as the column names
• Each value is separated by a comma, and text values are enclosed in single quotes
• The command ends with a semicolon

Common Mistakes

• Failing to match the column names and values in the INSERT INTO command
• Not enclosing text values in single quotes
• Not specifying values for mandatory columns

Retrieving Data

• The SELECT command is used to retrieve data from a table
• The command starts with SELECT followed by the column names to be retrieved
• The FROM clause specifies the table name
• The command ends with a semicolon
• The result set is displayed in MySQL Workbench

Understanding Entity Attributes

• Attributes are the data items you want to store about the entity (e.g., title, author, price)
• You need to know the name of the attribute (e.g., title) and the data type (e.g., text, number, date)
• You also need to decide on the length of the attribute (e.g., how long the title can be)

Importance of Practice

• Understanding the concept is one thing, but doing it is a different thing
• Practice creating tables and experimenting with different data types to learn more

Learn how to create and modify database tables, including identifying entities and attributes, deciding on columns and data types, and considering column size. Understand the different data types in MySQL for storing various types of data.