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Anonymous users2024-02-10Library|||1 (1 to 1) (1 to many.)
bai) (many-to-du) (entity).
2 (1 to many) (1 to 1) (many-to-many).
3 (multiple) (1 pcs).
4 (Database||.)zhidatabase) (database system dao|Inside|database system) (database management system||database manager system)[|Represent or allow, the left and right answers are optional 1].
5 (secondary image).
6 (relational model) (hierarchical model) (mesh model).
7 (record) (row) (element) [not sure, it's my own understanding] 8 (field) (column) (tuple).
9 (attribute set) (
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Anonymous users2024-02-09Since the first address is 100, the fifth element is equivalent to the first address + 4, so it is equal to 100 + (5-1) * 2 = 108
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Anonymous users2024-02-08A data dictionary is a directory of records of database and application metadata that users can access. An active data dictionary is a data dictionary whose contents can be automatically updated by the DBMS when changes are made to the database or application structure. A passive data dictionary is a data dictionary whose contents must be manually updated when modified.
The composition of a data dictionary: 1, data items 2, data structures 3, data flow 4, data storage 5, processing process.
A data item is the smallest unit discussed in a data structure and is the most basic, indivisible, named unit of data in a data record.
A data structure is the way a computer stores and organizes data. A data structure is a collection of data elements that have one or more specific relationships with each other.
A data stream was originally a concept used in the field of communications to represent a digitally encoded sequence of signals for information used in transmission.
The data storage is the temporary file generated by the data stream during the machining process or the information that needs to be found during the machining process. The data is recorded in some format on a computer's internal or external storage media. The data store should be named, and this naming should reflect the composition and meaning of the information features.
The data flow reflects the data flowing in the system and exhibits the characteristics of dynamic data. Data storage reflects the data at rest in the system and exhibits the characteristics of static data.
The specific processing logic of the processing process is generally described by a decision table or a decision tree.
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The result of the formula is within the range of values on the left.
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