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。
The “INDEXED BY index-name” clause states that a named index is required to find the values in the previous table.
If the index name index-name does not exist or cannot be used for the query, then the preparation of the SQLite statement fails.
The “NOT INDEXED” clause states that indexes are not used when accessing previous tables, including implicit indexes created by UNIQUE and PRIMARY KEY constraints.
However, even if “NOT INDEXED” is specified, INTEGER PRIMARY KEY can still be used to find entries. The following is Suppose there is a table. Use now 1.36.1. Grammar ¶
INDEXED BY The syntax of the clause, which can be associated with DELETE 、 UPDATE Or SELECT Statement to use together:SELECT|DELETE|UPDATE column1, column2... INDEXED BY (index_name) table_name WHERE (CONDITION);
1.36.2. Example ¶
COMPANY We will create an index and use it to INDEXED BY Operation.sqlite> CREATE INDEX salary_index ON COMPANY(salary); sqlite>
INDEXED BY Clause slave table COMPANY Select the data in, as follows:sqlite> SELECT * FROM COMPANY INDEXED BY salary_index WHERE salary > 5000;