The brief questions of previous years do not apply to this year , You should also recite the short answer questions in the two question banks in Baidu online disk that I share ( Link to the first blog in the database )

Chapter I

1. What is the definition of a database ?

         The database is stored in the computer for a long time , organized , A collection of large amounts of data that can be shared .

2. What are the main functions of the database management system

(1) Data definition function ,

(2) Organization of data , Storage and management ,

(3) Data manipulation function ,

(4) Transaction management and operation management of database ,

(5) Establishment and maintenance of database ,

(6) Other functions .

3. What are the three elements of the data model ?

         data structure , Data operation and data integrity constraints constitute the three elements of the data model .

4. What are the data operations in the database ?

         Data operations in the database include inserting , modify , Delete and query .

5. What are the three types of relationships between entities ?

         Relationships between entities include one-to-one relationships , One to many connection and many to many connection .

6. What are the common logical data models in the database field ?

         The logical data model commonly used in database field is hierarchical model , Reticular model , relational model , Object oriented model, etc .

7. What are the components of the database system ?

         Database system consists of database , Database management system , Application system and database administrator .

8. Three level structure of database system ?

         The three-level schema structure of database system refers to external schema , pattern , Internal mode

 

9. Database management system

Database management system (Database Management
System,DBMS) Is a layer of data management software between the user and the operating system , Provide a method for users or applications to access the database , Including the establishment of database , query , Update and various data control .DBMS Always based on some kind of data model , Can be divided into hierarchical models , Reticular model , relational model , Object oriented model, etc DBMS

10.
Data independence refers to the mutual independence between applications and data , Unaffected . Data independence is divided into physical data independence and logical data independence .(1) Logical independence : When the mode changes , The database administrator modifies the relevant external schema / Pattern mapping , Leave external mode unchanged , So that the application does not have to be modified , Ensure the logical independence of data and program , Abbreviation: logical independence of data .(2) Physical independence : When the storage structure of the database changes , Database administrator modify mode / Inner mode mapping , Leave mode unchanged , Application unaffected . Ensure the physical independence of data and program , Abbreviation: physical independence of data

Chapter II

1. What are the three components of the relational model ?

         Relational model consists of relational data structure , Relationship operation and relationship integrity constraints consist of three parts .

2.  What are the three types of integrity of relational models ?

         The integrity constraints of relationships include primary key constraints , Foreign key constraints and user-defined integrity constraints .

3. Query operations of which relationships are provided in relational algebra ?

         Queries in relational algebra include union of relations , hand over , difference , Cartesian product , choice , Projection , Operations such as join and division .

Chapter III

1.SQL What are the commonly used statements in the language ?

        SQL Language set data definitions , Data query , Integration of data manipulation and data control functions , The main operation statements include
CREATE,ALTER,DROP,INSERT,UPDATE,DELETE,SELECT,GRANT,REVOKE etc .

2.SQL Which common aggregate functions are available in ? How they are used ?

        SQL Some aggregate functions are provided in , Except for statistical database data , include COUNT,AVG,SUM, MAX,MIN etc. ,
COUNT(*) Out of usage , Null values are ignored in Statistics , use DISTINCT Option ignored Statistics on duplicate data . Aggregate functions can only be used with SELECT Clauses and HAVING clause .

3. What is a join query ? How connection queries specify connection conditions ?

         If a query involves two tables at the same time , It is called connection query . The connection conditions of connection query can be found in the WHERE Clause is specified by a comparison operation , Or at FROM
Clause specifies both the connection method and the connection condition .

4. What is a subquery ? Used in WHERE There are several ways to call a subquery in a clause ?

         Subquery is also called nested query , Is nested in SELECT,INSERT,UPDATE,DELETE Etc of SELECT Query statement . Multi use in
WHERE In Clause , Use the results of subqueries as search criteria . stay Where There are several ways to use subqueries in Clauses : from IN
Export sub query , Export subquery by comparison operator , from EXISTS Export sub query .

Chapter V

1. What is database integrity ? What are the types of relational database integrity ?

         Data integrity refers to the logical consistency and correctness of the data in the database .

         Relational database integrity includes entity integrity , Reference integrity and user-defined integrity .

2. The five common constraints are : Primary key constraint , Foreign key constraint , Non empty constraint , Unique constraint , Check constraints !

 

Chapter VII    

1. What technologies and knowledge are involved in database design ?

          Database design involves various technologies and knowledge , Including basic knowledge of computer , Methods and skills of programming , Principles and methods of software engineering , Basic knowledge of database , Knowledge of database design technology and application field .

2. What are the phases of database design ?

         Database design including requirements analysis , Conceptual structure design , Logical structure design , Physical structure design , Six stages of database implementation and database operation and maintenance .

3. establish E-R What steps does the diagram include ?

         establish E-R The process of drawing includes :(1) First determine the actual shape ,(2) Determine contact type ,(3) Solid body type And connections E-R chart ,(4) Determine the attributes of entity type and relation

 

Fill in the blanks in previous years

* The database is stored in the computer for a long time , organized , A collection of large amounts of data that can be shared .
* The functions of the database system include : Definition of database , Organization, storage and management of database , Manipulation of database , Management and operation management of database affairs , Establishment and maintenance of database
* Manipulation of the database includes inserting , delete , Modification and query
* data structure , Data manipulation and integrity constraints constitute the three elements of a data model
* Exercises between entities include one-to-one connections , One to many contact , Many to many connections
* The logical data model commonly used in database system is hierarchical model , Reticular model , relational model , Object oriented model, etc
*   Database system consists of database , Database management system , Application system and database administrator .
* The three-level schema structure of database system refers to schema , Internal mode and external mode .
*   Database management system (Database Management System,DBMS) Is located between the user and the operating system
          One layer data management software between , Provide a method for users or applications to access the database , Including the establishment of database ,

          query , Update and various data control .DBMS Always based on some kind of data model , Can be divided into hierarchical models , Reticular model ,            relational model , Object oriented model, etc
DBMS.

10.  Data independence refers to the mutual independence between applications and data , Unaffected . Data independence is divided into physical data independence         And logical data independence .

(1) Logical independence : When the mode changes , The database administrator modifies the relevant external schema / Pattern mapping , Make out mode          
  remain unchanged , So that the application does not have to be modified , Ensure the logical independence of data and program , Logic of abbreviated data Independence .

(2) Physical independence : When the storage structure of the database changes , Database administrator modify mode / Inner mode mapping , Enable mode protection          
  Remain unchanged , Application unaffected . Ensure the physical independence of data and program , Abbreviation: physical independence of data .

11. Relational model consists of relational data structure , Relationship operation and relationship integrity constraints consist of three parts .

12. Relationship integrity constraints include primary key constraints , Foreign key constraints and user-defined integrity constraints .

13. Queries in relational algebra include union of relations , hand over , difference , Cartesian product , choice , Projection , Operations such as join and division

14. SQL Language set data query , Data manipulation , Integration of data definition and data control functions , Its main operating language

         Sentence includes CREATE,ALTER,DROP,INSERT,UPDATE,DELETE,SELECT,GRANT,

        REVOKE etc .

15. SQL Some aggregate functions are provided in , For statistical database data , include COUNT,AVG,SUM,MAX,               MIN  etc. , except
COUNT(*) Out of usage , Null values are ignored in Statistics , use DISTINCT Option ignored

         Statistics on duplicate data . Aggregate rows can only be used for SELECT Clauses and HAVING clause .

16. If a query involves two tables at the same time , It is called connection query . The connection conditions of connection query can be found in the WHERE In Clause         Specified by a comparison operation , Or at FROM
Clause specifies both the connection method and the connection condition .

17. Subquery is also called nested query , Is nested in SELECT,INSERT,UPDATE,DELETE Etc       SELECT Query statement . Multi use in
WHERE In Clause , Use the results of subqueries as search criteria . stay Where

       There are several ways to use subqueries in Clauses : from IN Export sub query , Export subquery by comparison operator , from EXISTS        Export sub query .

18. Database security refers to protecting the database , Prevent data leakage caused by users' illegal use of the database , Change or destroy .

    The common security control methods in database systems include user identification and authentication , access control , Define view , audit , number      Data encryption, etc .

19. Data integrity refers to the logical consistency and accuracy of data in the database .

      Relational database integrity includes entity integrity , Reference integrity and user-defined integrity .

20. trigger (Trigger) It is a kind of special event driven stored procedure defined by the user on the relational table . trigger

      Insert table by , Modify and delete event activation .

21. Database design including requirements analysis , Conceptual structure design , Logical structure design , Physical structure design , database

       Implementation and database operation and maintenance .

22. establish E-R The process of drawing includes :(1) First determine the actual shape ,(2) Determine contact type ,(3) Solid body type

       And connections E-R chart ,(4) Determine the attributes of entity type and relation

 

 

Technology