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。
This chapter will show you the simple but useful commands used by SQLite programmers. These commands are called SQLite dot commands, and they differ in that they do not end with a semicolon.
Let’s type a simple sqlite3 Command, from the SQLite command prompt, you can use various SQLite commands.
$ sqlite3 SQLite version 3.3.6 Enter ".help" for instructions sqlite> For a list of available dot commands, you can type “.help” at any time. For example:
sqlite>.help The above command displays a list of various important SQLite point commands, as follows:
Command | Description |
|---|---|
.backup? DB? FILE | Back up the DB database (default is “main”) to the FILE file. |
.resume ON | OFF | Stop when an error occurs. The default is OFF. |
.databases | Lists the name of the database and the files it is attached to. |
.dump? TABLE? | Dump the database in SQL text format. If the TABLE table is specified, only TABLE tables that match the LIKE schema are dumped. |
.echo ON | OFF | Turns the echo command on or off. |
.exit | Exit the SQLite prompt. |
.explain ON | OFF | Turns on or off the output mode suitable for EXPLAIN. If there is no parameter, it is EXPLAIN on, that is, EXPLAIN is enabled. |
.header (s) ON | OFF | Turn the head display on or off. |
.help | Displays a message. |
.import FILE TABLE | Import data from the FILE file into the TABLE table. |
.indices? TABLE? | Displays the names of all indexes. If the TABLE table is specified, only the indexes of the TABLE table that match the LIKE schema are displayed. |
.load FILE? ENTRY? | Load an extended library. |
.log FILE | off | Turns the log on or off. The FILE file can be stderr (standard error) / stdout (standard output). |
.mode MODE | To set the output mode, MODE can be one of the following: |
Csv comma separated values | |
Column left-aligned column | |
< table > code for html HTML | |
SQL insert (insert) statement of insert TABLE table | |
One value per row for line | |
List values delimited by a .comparator string | |
Tabs values separated by Tab | |
Tcl TCL list element | |
.nullvalue STRING | Output the STRING string at the NULL value. |
.output FILENAME | Send the output to a FILENAME file. |
.output stdout | Send the output to the screen. |
.print STRING… | Output the STRING string verbatim. |
.prompt MAIN CONTINUE | Replace the standard prompt. |
.quit | Exit the SQLite prompt. |
.read FILENAME | Execute the SQL in the FILENAME file. |
.schema? TABLE? | Displays the CREATE statement. If the TABLE table is specified, only TABLE tables that match the LIKE schema are displayed. |
.separator STRING | Change the output mode and the delimiter used by .import. |
.show | Displays the current values of various settings. |
.stats ON | OFF | Turns statistics on or off. |
.tables? PATTERN? | Lists the names of tables that match the LIKE schema. |
.timeout MS | Try to open the locked table MS for milliseconds. |
.width NUM NUM | Sets the column width for column mode. |
.timer ON | OFF | Turns the CPU timer on or off. |
Let’s try to use the .show Command to view the default settings of the SQLite command prompt.
sqlite>.show echo: off explain: off headers: off mode: column nullvalue: "" output: stdout separator: "|" width: sqlite> Make sure there is no space between the sqlite > prompt and the dot command, otherwise it will not work properly. You can use the following point commands to format the output to the format listed below in this tutorial: The above settings will produce output in the following format: The key information of the database table is stored in the main table and named sqlite_master . To view the table summary, do the following: This will produce the following results: 1.4.1. Formatted output ¶
sqlite>.header on sqlite>.mode column sqlite>.timer on sqlite>
ID NAME AGE ADDRESS SALARY ---------- ---------- ---------- ---------- ---------- 1 Paul 32 California 20000.0 2 Allen 25 Texas 15000.0 3 Teddy 23 Norway 20000.0 4 Mark 25 Rich-Mond 65000.0 5 David 27 Texas 85000.0 6 Kim 22 South-Hall 45000.0 7 James 24 Houston 10000.0 CPU Time: user 0.000000 sys 0.000000
1.4.2.
sqlite_master Form ¶ sqlite>.schema sqlite_master
CREATE TABLE sqlite_master ( type text, name text, tbl_name text, rootpage integer, sql text );