5. Postgresql

  • 5.19. PostgreSQL UPDATE statement

    If we want to update the data in the PostgreSQL database, we can use the UPDATE To operate. 5.19.1. Grammar ¶ The...
    2025-10-25 13:32:24 UTC
  • 5.20. PostgreSQL DELETE statement

    You can use the DELETE statement to delete the data in the PostgreSQL table. 5.20.1. Grammar ¶ The following is the...
    2025-10-25 13:32:25 UTC
  • 5.21. PostgreSQL LIKE clause

    In the PostgreSQL database, if we want to get data that contains certain characters, we can use the LIKE Clause. In LI...
    2025-10-25 13:32:24 UTC
  • 5.22. PostgreSQL LIMIT clause

    In PostgreSQL limit Clause is used to limit the amount of data queried in a SELECT statement. 5.22.1. Grammar ¶ T...
    2025-10-25 13:32:22 UTC
  • 5.23. PostgreSQL ORDER BY statement

    In PostgreSQL ORDER BY Used to sort one or more columns of data in ascending (ASC) or descending (DESC) order. 5.23.1....
    2025-10-25 13:32:25 UTC
  • 5.24. PostgreSQL GROUP BY statement

    In PostgreSQL GROUP BY Statement and SELECT Statement to group the same data. GROUP BY is in a SELECT Statement,...
    2025-10-25 13:32:25 UTC
  • 5.25. PostgreSQL WITH clause

    In PostgreSQL WITH Clause provides a way to write auxiliary statements for use in larger queries. WITH Clauses hel...
    2025-10-25 13:32:25 UTC
  • 5.27. PostgreSQL DISTINCT keyword

    In PostgreSQL DISTINCT Keywords vs. SELECT Statement to remove duplicate records and get only unique records. When...
    2025-10-25 13:32:23 UTC
  • 5.28. PostgreSQL constraint

    PostgreSQL constraints are used to specify data rules in a table. If there is a data behavior that violates the constraint...
    2025-10-25 13:32:26 UTC
  • 5.29. PostgreSQL connection (JOIN)

    The PostgreSQL JOIN clause is used to combine rows from two or more tables based on common fields between those tables. In...
    2025-10-25 13:32:23 UTC
  • 5.30. PostgreSQL UNION operator

    The PostgreSQL UNION operation matches the result of combining two or more SELECT statements. The UNION operator is used t...
    2025-10-25 13:32:26 UTC
  • 5.31. PostgreSQL NULL value

    NULL The value represents missing unknown data. By default, the columns of a table can be stored NULL Value. Thi...
    2025-10-25 13:32:25 UTC
  • 5.32. PostgreSQL alias

    We can rename the name of a table or field with SQL, which is the alias of the table or field. Aliases are created to make...
    2025-10-25 13:32:22 UTC
  • 5.33. PostgreSQL trigger

    The PostgreSQL trigger is the callback function of the database, which is automatically executed / called when the specified...
    2025-10-25 13:32:26 UTC
  • 5.34. PostgreSQL index

    Index is a special table query that accelerates search engines to retrieve data. Simply put, an index is a pointer to the da...
    2025-10-25 13:32:25 UTC
  • 5.35. PostgreSQL ALTER TABLE command

    In PostgreSQL ALTER TABLE The command is used to add, modify, and delete a column that already exists in a table. Beside...
    2025-10-25 13:32:23 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。