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Relational schemas - Primary key.pdf
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- 7. Relational Schemas: PrimaryKey these tables have a tabular shape
- 8. Relational Schemas: PrimaryKey these tables have a tabular form a relational schema can be applied to represent them
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- 10. Relational Schemas: PrimaryKey sales per customer of our company
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- 12. Relational Schemas: PrimaryKey the dates of a few purchases may coincide
- 13. Relational Schemas: PrimaryKey the ID of a customer may appear a few times
- 14. Relational Schemas: PrimaryKey there is a possibility to see the same item code a few times
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- 16. Relational Schemas: PrimaryKey all the numbers in this column will be different
- 17. Relational Schemas: PrimaryKey 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
- 18. Relational Schemas: PrimaryKey Primary Key
- 19. Relational Schemas: PrimaryKey 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
- 20. Relational Schemas: PrimaryKey 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
- 21. Relational Schemas: PrimaryKey - 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
- 22. Relational Schemas: PrimaryKey - 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
- 23. Relational Schemas: PrimaryKey Primary Key may be composed of a set of columns
- 24. Relational Schemas: PrimaryKey Primary Key may be composed of a set of columns e.g. “purchase_number” + “date_of_purchase”
- 25. Relational Schemas: PrimaryKey Primary Key may be composed of a set of columns e.g. “purchase_number” + “date_of_purchase”
- 26. Relational Schemas: PrimaryKey Primary Key one-column primary key = all purchases will be recorded under a different number
- 27. Relational Schemas: PrimaryKey - 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
- 28. Relational Schemas: PrimaryKey - 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
- 29. Relational Schemas: PrimaryKey - 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
- 30. Relational Schemas: PrimaryKey Primary Key
- 31. Relational Schemas: PrimaryKey Primary Key
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- 34. Table name: Sales Primarykey: purchase_number Other fields: date_of_purchase, customer_id, item_code Relational Schemas: Primary Key
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- 36. - each tablecan 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
- 37. - each tablecan 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
- 38. relational schema Relational Schemas:Primary Key
- 39. database schema Relational Schemas:Primary Key
- 40. database schema (relational schemas) RelationalSchemas: Primary Key
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- 52. Relational Schemas: ForeignKey always look for the foreign keys, as they show us where the relations are
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- 56. Relational Schemas: ForeignKey no repeating and missing values
- 57. Relational Schemas: ForeignKey no repeating and missing values (unique values only)
- 58. Relational Schemas: ForeignKey no repeating and missing values repeating and missing values (unique values only)
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- 60. Relational Schemas: ForeignKey ERROR
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- 64. Relational Schemas: ForeignKey no repeating and missing values
- 65. Relational Schemas: ForeignKey no repeating and missing values repeating and missing values
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- 69. Relational Schemas: ForeignKey identifies the relationships between tables, not the tables themselves foreign key
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- 71. Relational Schemas: UniqueKey & Null Values
- 72. Relational Schemas: UniqueKey & Null Values
- 73. Relational Schemas: UniqueKey & Null Values ?
- 74. Relational Schemas: UniqueKey & Null Values
- 75. You can havetwo or more companies with the same name Relational Schemas: Unique Key & Null Values
- 76. Relational Schemas: UniqueKey & Null Values
- 77. You cannot havetwo US numbers that are completely identical Relational Schemas: Unique Key & Null Values
- 78. ? Relational Schemas: UniqueKey & Null Values
- 79. used whenever youwould like to specify that you don’t want to see duplicate data in a given field unique key Relational Schemas: Unique Key & Null Values
- 80. Relational Schemas: UniqueKey & Null Values unique key primary key NULL VALUES no yes
- 81. Relational Schemas: UniqueKey & Null Values
- 82. Relational Schemas: UniqueKey & Null Values
- 83. Relational Schemas: UniqueKey & Null Values ERROR
- 84. Relational Schemas: UniqueKey & Null Values unique key primary key NULL VALUES no yes NUMBER OF KEYS 1 0, 1, 2…
- 85. Relational Schemas: UniqueKey & Null Values unique key primary key NULL VALUES no yes NUMBER OF KEYS 1 0, 1, 2… APPLICATION TO MULTIPLE COLUMNS yes yes
- 86. Relational Schemas: UniqueKey & Null Values
- 87. Relational Schemas: UniqueKey & Null Values
- 88. Relational Schemas: UniqueKey & Null Values
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- 91. Relationships Relationships relationships tell youhow 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
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- 97. unique values repeated values onevalue from the customer_id column under the “Customers” table can be found many times in the customer_id column in the “Sales” table. one-to-many type of relationship Relationships
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- 103. 1 customer 1 purchase or>1 purchase Relationships
- 104. 1 customer 1 purchase or>1 purchase Relationships
- 105. 1 customer 1 purchase or>1 purchase minimum # of instances of the “Customers” table that can be associated with the “Sales” entity Relationships
- 106. 1 customer 1 purchase or>1 purchase 1 minimum # of instances of the “Customers” table that can be associated with the “Sales” entity Relationships
- 107. 1 customer 1 purchase or>1 purchase Relationships
- 108. 1 customer 1 purchase or>1 purchase maximum # of instances of the “Customers” table that can be associated with the “Sales” entity Relationships
- 109. 1 customer 1 purchase or>1 purchase maximum # of instances of the “Customers” table that can be associated with the “Sales” entity many Relationships
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- 114. 1 customer 1 purchaseminimum = Relationships
- 115. 1 customer 1 purchaseminimum = = maximum Relationships
- 116. 1 customer 1 purchaseminimum = = maximum Relationships
- 117. 1 customer 1 purchaseminimum = = maximum Relationships
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- 120. Customers to Sales:one-to-many Relationships
- 121. Customers to Sales:one-to-many Relationships
- 122. Customers to Sales:one-to-many Sales to Customers: many-to-one Relationships
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- 126. Relationships relationships tell youhow 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
- 127. Relationships relationships tell youhow 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
- 128. Relationships relationships tell youhow 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
- 129. Relationships relationships tell youhow 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
- 130. Relationships relationships tell youhow 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
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- 132. Relational schemas - representthe concept database administrators must implement Relationships
- 133. Relational schemas - representthe concept database administrators must implement - depict how a database is organized Relationships
- 134. Relational schemas - representthe concept database administrators must implement - depict how a database is organized = blueprints, or a plan for a database Relationships
- 135. Relational schemas - representthe 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