Relational schemas - Primary key.pdf
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Aug 07, 2023
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About This Presentation
Relational schemas - Primary key
Slide Content
Basic Database Terminology
Relational Schemas: Primary Key
Relational Schemas: Primary Key
Relational Schemas: Primary Key
Relational Schemas: Primary Key
Relational Schemas: Primary Key
Relational Schemas: Primary Key
these tables have a tabular shape
these tables have a tabular shape
Relational Schemas: Primary Key
these tables have a tabular form
a relational schema can be applied to represent them
these tables have a tabular form
a relational schema can be applied to represent them
Relational Schemas: Primary Key
Relational Schemas: Primary Key
sales per customer of our company
sales per customer of our company
Relational Schemas: Primary Key
Relational Schemas: Primary Key
the dates of a few purchases may coincide
the dates of a few purchases may coincide
Relational Schemas: Primary Key
the ID of a customer may appear a few times
the ID of a customer may appear a few times
Relational Schemas: Primary Key
there is a possibility to see the same item code a few times
there is a possibility to see the same item code a few times
Relational Schemas: Primary Key
Relational Schemas: Primary Key
all the numbers in this column will be different
all the numbers in this column will be different
Relational Schemas: Primary Key
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
primary key
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
primary key
Relational Schemas: Primary Key
Primary Key
Primary Key
Relational Schemas: Primary Key
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
Primary Key
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
Primary Key
Relational Schemas: Primary Key
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
Primary Key
-each table can have one and only one primary key
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
Primary Key
-each table can have one and only one primary key
Relational Schemas: Primary Key
-each table can have one and only one primary key
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
Primary Key
-in one table, you cannot have 3 or 4 primary keys
-each table can have one and only one primary key
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
Primary Key
-in one table, you cannot have 3 or 4 primary keys
Relational Schemas: Primary Key
-each table can have one and only one primary key
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
Primary Key
-in one table, you cannot have 3 or 4 primary keys
-each table can have one and only one primary key
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
Primary Key
-in one table, you cannot have 3 or 4 primary keys
Relational Schemas: Primary Key
Primary Key
may be composed of a set of columns
Primary Key
may be composed of a set of columns
Relational Schemas: Primary Key
Primary Key
may be composed of a set of columns
e.g. “purchase_number” + “date_of_purchase”
Primary Key
may be composed of a set of columns
e.g. “purchase_number” + “date_of_purchase”
Relational Schemas: Primary Key
Primary Key
may be composed of a set of columns
e.g. “purchase_number” + “date_of_purchase”
Primary Key
may be composed of a set of columns
e.g. “purchase_number” + “date_of_purchase”
Relational Schemas: Primary Key
Primary Key
one-column primary key = all purchases will be recorded under a
different number
Primary Key
one-column primary key = all purchases will be recorded under a
different number
Relational Schemas: Primary Key
-each table can have one and only one primary key
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
Primary Key
-in one table, you cannot have 3 or 4 primary keys
-each table can have one and only one primary key
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
Primary Key
-in one table, you cannot have 3 or 4 primary keys
Relational Schemas: Primary Key
-each table can have one and only one primary key
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
Primary Key
-primary keys are the unique identifiers of a table
-in one table, you cannot have 3 or 4 primary keys
-each table can have one and only one primary key
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
Primary Key
-primary keys are the unique identifiers of a table
-in one table, you cannot have 3 or 4 primary keys
Relational Schemas: Primary Key
-each table can have one and only one primary key
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
Primary Key
-primary keys are the unique identifiers of a table
-cannot contain null values!
-in one table, you cannot have 3 or 4 primary keys
-each table can have one and only one primary key
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
Primary Key
-primary keys are the unique identifiers of a table
-cannot contain null values!
-in one table, you cannot have 3 or 4 primary keys
Relational Schemas: Primary Key
Primary Key
Primary Key
Relational Schemas: Primary Key
Primary Key
Primary Key
Relational Schemas: Primary Key
Relational Schemas: Primary Key
Table name: Sales
Primary key: purchase_number
Other fields: date_of_purchase, customer_id, item_code
Relational Schemas: Primary Key
Primary key: purchase_number
Other fields: date_of_purchase, customer_id, item_code
Relational Schemas: Primary Key
=
Relational Schemas: Primary Key
Relational Schemas: Primary Key
-each table can have one and only one primary key
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
Primary Key
-primary keys are the unique identifiers of a table
-cannot contain null values!
Relational Schemas: Primary Key
-in one table, you cannot have 3 or 4 primary keys
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
Primary Key
-primary keys are the unique identifiers of a table
-cannot contain null values!
Relational Schemas: Primary Key
-in one table, you cannot have 3 or 4 primary keys
-each table can have one and only one primary key
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
Primary Key
-primary keys are the unique identifiers of a table
-cannot contain null values!
-not all tables you work with will have a primary key
Relational Schemas: Primary Key
-in one table, you cannot have 3 or 4 primary keys
a column (or a set of columns) whose value exists and is unique for
every record in a table is called a primary key
Primary Key
-primary keys are the unique identifiers of a table
-cannot contain null values!
-not all tables you work with will have a primary key
Relational Schemas: Primary Key
-in one table, you cannot have 3 or 4 primary keys
relational schema
Relational Schemas: Primary Key
Relational Schemas: Primary Key
database schema
Relational Schemas: Primary Key
Relational Schemas: Primary Key
database schema
(relational schemas)
Relational Schemas: Primary Key
(relational schemas)
Relational Schemas: Primary Key
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
always look for the foreign keys, as
they show us where the relations are
always look for the foreign keys, as
they show us where the relations are
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
no repeating and missing values
no repeating and missing values
Relational Schemas: Foreign Key
no repeating and missing values
(unique values only)
no repeating and missing values
(unique values only)
Relational Schemas: Foreign Key
no repeating and missing values
repeating and missing values
(unique values only)
no repeating and missing values
repeating and missing values
(unique values only)
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
ERROR
ERROR
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
no repeating and missing values
no repeating and missing values
Relational Schemas: Foreign Key
no repeating and missing values
repeating and missing values
no repeating and missing values
repeating and missing values
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
Relational Schemas: Foreign Key
identifies the relationships between tables, not the tables themselves
foreign key
identifies the relationships between tables, not the tables themselves
foreign key
Relational Schemas: Foreign Key
Relational Schemas: Unique Key & Null Values
Relational Schemas: Unique Key & Null Values
Relational Schemas: Unique Key & Null Values
?
?
Relational Schemas: Unique Key & Null Values
You can have two or more
companies with the same name
Relational Schemas: Unique Key & Null Values
companies with the same name
Relational Schemas: Unique Key & Null Values
Relational Schemas: Unique Key & Null Values
You cannothave two US numbers that are completely identical
Relational Schemas: Unique Key & Null Values
Relational Schemas: Unique Key & Null Values
?
Relational Schemas: Unique Key & Null Values
Relational Schemas: Unique Key & Null Values
used whenever you would like to specify that you don’t want to see
duplicate data in a given field
unique key
Relational Schemas: Unique Key & Null Values
duplicate data in a given field
unique key
Relational Schemas: Unique Key & Null Values
Relational Schemas: Unique Key & Null Values
unique keyprimary key
NULL VALUES no yes
unique keyprimary key
NULL VALUES no yes
Relational Schemas: Unique Key & Null Values
Relational Schemas: Unique Key & Null Values
Relational Schemas: Unique Key & Null Values
ERROR
ERROR
Relational Schemas: Unique Key & Null Values
unique keyprimary key
NULL VALUES no yes
NUMBER OF KEYS 1 0, 1, 2…
unique keyprimary key
NULL VALUES no yes
NUMBER OF KEYS 1 0, 1, 2…
Relational Schemas: Unique Key & Null Values
unique keyprimary key
NULL VALUES no yes
NUMBER OF KEYS 1 0, 1, 2…
APPLICATION TO
MULTIPLE COLUMNS
yes yes
unique keyprimary key
NULL VALUES no yes
NUMBER OF KEYS 1 0, 1, 2…
APPLICATION TO
MULTIPLE COLUMNS
yes yes
Relational Schemas: Unique Key & Null Values
Relational Schemas: Unique Key & Null Values
Relational Schemas: Unique Key & Null Values
Relationships
Relationships
Relationships
Relationships
Relationships
Relationships
relationships tell you how much of the data from a foreign key field can
be seen in the primary key column of the table the data is related to
and vice versa
Relationships
relationships tell you how much of the data from a foreign key field can
be seen in the primary key column of the table the data is related to
and vice versa
Relationships
Relationships
unique values
Relationships
Relationships
unique values
Relationships
Relationships
unique values
repeated values
Relationships
repeated values
Relationships
unique values
repeated values
onevalue from the customer_idcolumn under the “Customers” table can
be found manytimes in the customer_idcolumn in the “Sales” table.
one-to-many type of relationship
Relationships
repeated values
onevalue from the customer_idcolumn under the “Customers” table can
be found manytimes in the customer_idcolumn in the “Sales” table.
one-to-many type of relationship
Relationships
Relationships
Relationships
Relationships
1 customer
Relationships
Relationships
1 customer1 purchase
Relationships
Relationships
1 customer1 purchase
or >1 purchase
Relationships
or >1 purchase
Relationships
1 customer1 purchase
or >1 purchase
Relationships
or >1 purchase
Relationships
1 customer1 purchase
or >1 purchase
minimum # of instances of the
“Customers” table that can be
associated with the “Sales” entity
Relationships
or >1 purchase
minimum # of instances of the
“Customers” table that can be
associated with the “Sales” entity
Relationships
1 customer1 purchase
or >1 purchase
1
minimum # of instances of the
“Customers” table that can be
associated with the “Sales” entity
Relationships
or >1 purchase
1
minimum # of instances of the
“Customers” table that can be
associated with the “Sales” entity
Relationships
1 customer1 purchase
or >1 purchase
Relationships
or >1 purchase
Relationships
1 customer1 purchase
or >1 purchase
maximum # of instances of the
“Customers” table that can be
associated with the “Sales” entity
Relationships
or >1 purchase
maximum # of instances of the
“Customers” table that can be
associated with the “Sales” entity
Relationships
1 customer1 purchase
or >1 purchase
maximum # of instances of the
“Customers” table that can be
associated with the “Sales” entity
many
Relationships
or >1 purchase
maximum # of instances of the
“Customers” table that can be
associated with the “Sales” entity
many
Relationships
Relationships
Relationships
1 purchase
Relationships
Relationships
1 customer1 purchase
Relationships
Relationships
1 customer1 purchase minimum =
Relationships
Relationships
1 customer1 purchase minimum = = maximum
Relationships
Relationships
1 customer1 purchase minimum = = maximum
Relationships
Relationships
1 customer1 purchase minimum = = maximum
Relationships
Relationships
Relationships
Relationships
Customers to Sales:one-to-many
Relationships
Relationships
Customers to Sales:one-to-many
Relationships
Relationships
Customers to Sales:one-to-many
Sales to Customers:many-to-one
Relationships
Sales to Customers:many-to-one
Relationships
Relationships
cardinality constraints
Relationships
Relationships
cardinality constraints
MN
Relationships
MN
Relationships
Relationships
relationships tell you how much of the data from a foreign key field can
be seen in the primary key column of the table the data is related to
and vice versa
Relationships
relationships tell you how much of the data from a foreign key field can
be seen in the primary key column of the table the data is related to
and vice versa
Relationships
Relationships
relationships tell you how much of the data from a foreign key field can
be seen in the primary key column of the table the data is related to
and vice versa
types of relationships
Relationships
relationships tell you how much of the data from a foreign key field can
be seen in the primary key column of the table the data is related to
and vice versa
types of relationships
Relationships
Relationships
relationships tell you how much of the data from a foreign key field can
be seen in the primary key column of the table the data is related to
and vice versa
types of relationships
-one-to-many (many-to-one)
Relationships
relationships tell you how much of the data from a foreign key field can
be seen in the primary key column of the table the data is related to
and vice versa
types of relationships
-one-to-many (many-to-one)
Relationships
Relationships
relationships tell you how much of the data from a foreign key field can
be seen in the primary key column of the table the data is related to
and vice versa
types of relationships
-one-to-many (many-to-one)
-one-to-one
Relationships
relationships tell you how much of the data from a foreign key field can
be seen in the primary key column of the table the data is related to
and vice versa
types of relationships
-one-to-many (many-to-one)
-one-to-one
Relationships
Relationships
relationships tell you how much of the data from a foreign key field can
be seen in the primary key column of the table the data is related to
and vice versa
types of relationships
-one-to-many (many-to-one)
-one-to-one
-many-to-many
Relationships
relationships tell you how much of the data from a foreign key field can
be seen in the primary key column of the table the data is related to
and vice versa
types of relationships
-one-to-many (many-to-one)
-one-to-one
-many-to-many
Relationships
Relational schemas
Relationships
Relationships
Relational schemas
-represent the concept database administrators must implement
Relationships
-represent the concept database administrators must implement
Relationships
Relational schemas
-represent the concept database administrators must implement
-depict how a database is organized
Relationships
-represent the concept database administrators must implement
-depict how a database is organized
Relationships
Relational schemas
-represent the concept database administrators must implement
-depict how a database is organized
= blueprints, or a plan for a database
Relationships
-represent the concept database administrators must implement
-depict how a database is organized
= blueprints, or a plan for a database
Relationships
Relational schemas
-represent the concept database administrators must implement
-depict how a database is organized
= blueprints, or a plan for a database
-will help you immensely while writing your queries!
Relationships
-represent the concept database administrators must implement
-depict how a database is organized
= blueprints, or a plan for a database
-will help you immensely while writing your queries!
Relationships
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