Revisit "Introduction to Database System" [First Basics] [Chapter 5 Database Integrity]

The content of this article is the review notes of the self-study course "Introduction to Database System" by Professor Wang Shan and Sa Shixuan of Renmin University of China. The learning video comes from Xiaopo Station ( portal ), corresponding to video P32-P36, which belongs to the textbook "[First Basics]" "[Chapter 5 Database Integrity]" content.

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P32 database integrity overview and entity integrity

32.1 Integrity of the database

• The correctness of the data (the data must conform to the actual situation)
• Data compatibility (data in different relational tables for the same object is logical)

32.2 Physical integrity

• Definition code eg1:
  Define the Sno attribute in the Student table as a code
  
  eg2: Define the Sno, Cn oh attribute group in the SC table as a code
  
• Entity integrity check and default handling
  ① Check whether the master code value is unique, if not, refuse to insert or modify it
  ② Check whether each attribute of the master code is empty, and refuse to insert or modify as long as one of them is empty
  
  

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P33 Referential integrity

33.1 Referential integrity definition

33.2 Referential integrity check and default handling

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P34 User-defined integrity

34.1 Constraints on attributes

• Column value is not empty (NOT NULL)
  
• Unique column value (UNIQUE)
  
• Check whether the column value meets a conditional expression (CHECK phrase)
  

34.2 Constraints on Tuples

34.3 Summary and Comparison of Database Integrity

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P35 Integrity Constraint Naming Clauses and Assertions

35.1 Integrity Constraint Naming Clause

• Example eg: integrity constraint naming clause
  
• Example eg: modify the integrity restriction in the table
  

35.2 Affirmation

• Statement format for creating assertion

CREATE ASSERTION <断言名> <CHECK 子句>

• Example eg:
  
• Statement format for delete assertion

DROP ASSERTION <断言名>;

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P36 trigger

36.1 Trigger

• A special event-driven process defined by the user on the relational table ;
• Any user's addition, deletion or modification of the table will be automatically activated by the server to the corresponding trigger
• Triggers can try more complex inspections and operations, with more surprises and more powerful data control capabilities

36.2 Trigger operation

• Define triggers (can only be defined on the basic table )
  
  
• Activation trigger
  
• Delete trigger
  

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notes

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