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Match the following RDBMS integrity constraints with their descriptions:
Entity Integrity Constraints = Restrict the values in a row of an individual table Referential Integrity Constraints = Specifies that a row of one table that refers to another row must refer to an existing row in that table Domain Integrity Constraints = Includes Not null and Check constraints Key Constraints = Subcategory of Entity Integrity Constraints
Match the following characteristics of NULL value with their descriptions:
A NULL value distinct from zero or other numeric value for numerical data = Characteristic of NULL value A NULL value indicates ‘not applicable’, ‘missing’, or ‘not known’ = Characteristic of NULL value General-purpose programming = Python Client-side scripting for web applications = JavaScript
Match the following subcategories of Entity Integrity Constraints with their descriptions:
Domain Integrity Constraints = Subcategory of Entity Integrity Constraints Key Constraints = Subcategory of Entity Integrity Constraints Restrict the values in a row of an individual table = Entity Integrity Constraints Specifies that a row of one table that refers to another row must refer to an existing row in that table = Referential Integrity Constraints
Match the following general characteristics of Constraints provided by Oracle with their descriptions:
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Match the following descriptions of NOT NULL Constraints with their characteristics:
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Explain the two broad categories into which database integrity constraints can be classified.
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What are Entity Integrity Constraints and how are they further classified?
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What is the purpose of Referential Integrity Constraints?
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Explain the NOT NULL Constraints in Oracle and their characteristics.
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How are NULL values stored in Oracle and what do they represent?
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Study Notes
RDBMS Integrity Constraints
- Integrity constraints are rules to ensure data accuracy and consistency within a relational database management system (RDBMS).
- Common types include entity integrity, referential integrity, and domain integrity.
Characteristics of NULL Values
- NULL represents the absence of a value, not zero or an empty string.
- Queries with NULL values require special handling; operators like "=", "<>", or "IS NULL" behave differently.
- NULL can lead to complications in aggregate functions, as they are usually ignored.
Entity Integrity Constraints
- Ensure that each entity (row) in a table is unique and identifiable.
- Subcategories include:
- Primary Key Constraints: Enforce uniqueness for a column or set of columns.
- Unique Constraints: Guarantee that all values in a column are different but allow NULLs.
Oracle Constraints Characteristics
- Oracle databases provide comprehensive constraint definitions for data integrity.
- They include NOT NULL, UNIQUE, PRIMARY KEY, FOREIGN KEY, and CHECK constraints.
- Constraints can affect performance; excessive use may slow down operations due to overhead.
NOT NULL Constraints
- Prevent the insertion of NULL values in specified columns, ensuring data integrity.
- Commonly used for columns that require mandatory data entry.
- Helps enforce business rules by maintaining essential information.
Categories of Database Integrity Constraints
- Integrity constraints can be classified into two broad categories:
- Entity Integrity Constraints: Ensure uniqueness and validity of data entries.
- Referential Integrity Constraints: Maintain consistent references between related tables.
Purpose of Referential Integrity Constraints
- Protect relationships between tables by ensuring that foreign keys correspond to valid primary keys.
- Prevent orphan records, thus maintaining relational data integrity.
NOT NULL Constraints in Oracle
- NOT NULL constraints prevent columns from having a NULL value, mandating a valid entry.
- Ensures crucial information is always available for data processing and querying.
Storage of NULL Values in Oracle
- NULL values are stored by having a specific indicator flag rather than an actual value.
- Represent unknown or inapplicable information for a specific column.
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Description
Test your knowledge of database integrity constraints and object constraints in RDBMS with this quiz. Explore the rules that restrict values in a database and understand how Oracle's constraints align with the relational model. Assess your understanding of the classification and application of these constraints in the context of Oracle databases.