1. Sqlite

  • 1.19. SQLite Delete statement

    SQLite Of DELETE The query is used to delete existing records in the table. You can use the WHERE Of the clause ...
    2025-10-25 13:32:45 UTC
  • 1.20. SQLite Like clause

    SQLite Of LIKE Operator is a text value that matches the pattern specified by a wildcard. If the search expression mat...
    2025-10-25 13:32:46 UTC
  • 1.21. SQLite Glob clause

    SQLite’s GLOB Operator is a text value that matches the pattern specified by a wildcard. If the search expression matches ...
    2025-10-25 13:32:42 UTC
  • 1.23. SQLite Order By

    SQLite’s ORDER BY Clause is used to sort data in ascending or descending order based on one or more columns. 1.23.1. ...
    2025-10-25 13:32:45 UTC
  • 1.24. SQLite Group By

    SQLite’s GROUP BY Clause is used with SELECT Statement to group the same data. In SELECT Statement, the GROUP ...
    2025-10-25 13:32:43 UTC
  • 1.25. SQLite Having clause

    HAVING Clause allows you to specify conditions to filter the grouped results that will appear in the final result. W...
    2025-10-25 13:32:45 UTC
  • 1.26. SQLite Distinct keyword

    SQLite’s DISTINCT Keywords vs. SELECT Statement to eliminate all duplicate records and get only one record. It is po...
    2025-10-25 13:32:47 UTC
  • 1.27. SQLite PRAGMA

    SQLite’s PRAGMA The command is a special command that can be used to control various environment variables and status flag...
    2025-10-25 13:32:44 UTC
  • 1.28. SQLite constraint

    Constraints are rules that are enforced on the data columns of a table. These are used to limit the types of data that can b...
    2025-10-25 13:32:48 UTC
  • 1.29. SQLite Join

    SQLite’s Join Clause is used to combine records of tables in two or more databases. JOIN is a means of combining field...
    2025-10-25 13:32:42 UTC
  • 1.30. SQLite Unions clause

    SQLite’s UNION Clause / operator is used to merge two or more SELECT Statement and does not return any duplicate rows....
    2025-10-25 13:32:47 UTC
  • 1.31. SQLite NULL value

    SQLite’s NULL Is an item used to represent a missing value. One of the tables NULL A value is a value that appears bla...
    2025-10-25 13:32:42 UTC
  • 1.32. SQLite alias

    You can temporarily rename the table or column to another name, which is called 别名 . The use of a table alias refers to th...
    2025-10-25 13:32:45 UTC
  • 1.33. SQLite trigger (Trigger)

    SQLite 触发器(Trigger) Is a callback function for the database that is automatically executed / called when a specified datab...
    2025-10-25 13:32:44 UTC
  • 1.34. SQLite transaction (Transaction)

    A Transaction is a unit of work that performs work on a database. A Transaction is a unit or sequence of work that is comple...
    2025-10-25 13:32:43 UTC
  • 1.35. SQLite Index (Index)

    Index is a special look-up table, which is used by database search engine to speed up data retrieval. Simply put, an index i...
    2025-10-25 13:32:41 UTC
《地理信息系统原理、技术与方法》  97

最近几年来,地理信息系统无论是在理论上还是应用上都处在一个飞速发展的阶段。 GIS被应用于多个领域的建模和决策支持,如城市管理、区划、环境整治等等,地理信息成为信息时代重要的组成部分之一; “数字地球”概念的提出,更进一步推动了作为其技术支撑的GIS的发展。 与此同时,一些学者致力于相关的理论研究,如空间感知、空间数据误差、空间关系的形式化等等。 这恰好说明了地理信息系统作为应用技术和学科的两个方面,并且这两个方面构成了相互促进的发展过程。