The sqlite3 commnad line tool
- 1. The sqlite3 command line tool In this part of the SQLite tutorial, we will cover the sqlite3 command line tool. The manual describes the sqlite3 as follows: sqlite3 is a terminal-based front-end to the SQLite library that can evaluate queries interactively and display the results in multiple for‐ mats. sqlite3 can also be used within shell scripts and other applica‐ tions to provide batch processing features. sqlite3 tool sqlite3 is a terminal based frontend to the SQLite library that can evaluate queries interactively and display the results in multiple formats. It can also be used within scripts. On the terminal screen, we see the following prompt of the sqlite3 tool. $ sqlite3 test.db SQLite version 3.5.9 Enter ".help" for instructions sqlite> The .help is one of the meta commnads of the sqlite3 tool. It shows a list of them. The .exit and the The .quit commands exit the sqlite3 session. The .databases command shows the attached databases. The .tables command lists the available tables. Creating a database The complete SQLite database is stored in a single cross-platform disk file. We use the sqlite3
- 2. command line tool to create a new database file. $ sqlite3 movies.db Here we create a new movies.db database. If the exists, it is opened. Basic sqlite3 meta commnads Next we describe some of the meta commands of the sqlite3 tool. sqlite> .tables Books Customers Log Orders Testing Cars Friends Names Reservations The .tables commnad now shows the available tables. sqlite> SELECT * FROM Names; 1|Tom 2|Lucy 3|Frank 4|Jane 5|Robert Here we get the output of a simple SELECT statement. By default, the output mode is line and the separator is |.
- 3. sqlite> .separator : sqlite> SELECT * FROM Names; 1:Tom 2:Lucy 3:Frank 4:Jane 5:Robert Here we have used a new colon separator. There are several other output modes available. The following example will show the column output mode. sqlite> .mode column sqlite> .headers on sqlite> SELECT * FROM Names; Id Name ---------- ---------- 1 Tom
- 4. 2 Lucy 3 Frank 4 Jane 5 Robert In this example, we have our data in the column mode. Plus we show the column headers with the .headers command. By default, the headers are hidden. The .width command adjusts the size of the columns. sqlite> SELECT Title, Author FROM Books; Title Author ------------- ----------- War and Peace Leo Tolstoy The Brothers Fyodor Dost Crime and Pun Fyodor Dost Here, the column widths are not wide enough to display all data correctly. sqlite> .width 22, 18 sqlite> SELECT Title, Author FROM Books; Title Author
- 5. ---------------------- ------------------ War and Peace Leo Tolstoy The Brothers Karamazov Fyodor Dostoyevsky Crime and Punishment Fyodor Dostoyevsky Here we change the column widths. The first column will be 22 characters wide, the second 18. sqlite> .show echo: off explain: off headers: off mode: list nullvalue: "" output: stdout separator: "|" width: The .show command lists various settings. We can see the output mode, the separator used in the list mode, the headers.
- 6. sqlite> .schema Cars CREATE TABLE Cars(Id integer primary key, Name text, Cost integer); The .schema command shows the structure of the table. It gives the DDL SQL to create the table. Executing SQL from the shell We can execute SQL commands from the shell. $ sqlite3 test.db "SELECT * FROM Cars;" Id Name Cost ---------- ---------- ---------- 1 Audi 52642 2 Mercedes 57127 3 Skoda 9000 4 Volvo 29000 5 Bentley 350000 6 Citroen 21000 7 Hummer 41400 8 Volkswagen 21600
- 7. Here we have non interactively executed a SELECT SQL command. We selected all cars from the Cars table. Dumping tables It is possible to dump tables in SQL format to the disk. This way we can easily save the structure and the data of a database table. We have the Cars table. sqlite> SELECT * FROM Cars; Id Name Cost ---------- ---------- ---------- 1 Audi 52642 2 Mercedes 57127 3 Skoda 9000 4 Volvo 29000 5 Bentley 350000 6 Citroen 21000 7 Hummer 41400
- 8. 8 Volkswagen 21600 Now, we are going to use the .dump command to dump the table. sqlite> .dump Cars BEGIN TRANSACTION; CREATE TABLE Cars(Id integer primary key, Name text, Cost integer); INSERT INTO "Cars" VALUES(1,'Audi',52642); INSERT INTO "Cars" VALUES(2,'Mercedes',57127); INSERT INTO "Cars" VALUES(3,'Skoda',9000); INSERT INTO "Cars" VALUES(4,'Volvo',29000); INSERT INTO "Cars" VALUES(5,'Bentley',350000); INSERT INTO "Cars" VALUES(6,'Citroen',21000); INSERT INTO "Cars" VALUES(7,'Hummer',41400); INSERT INTO "Cars" VALUES(8,'Volkswagen',21600); COMMIT; The .dump command shows us the SQL necessary to recreate the table. sqlite> .output cars.sql
- 9. sqlite> .dump Cars We can also redirect the output to a file. The .output command will redirect the output to the cars.sql file. $ cat cars.sql BEGIN TRANSACTION; CREATE TABLE Cars(Id integer primary key, Name text, Cost integer); INSERT INTO "Cars" VALUES(1,'Audi',52642); ... We verify it. Reading SQL We can read SQL from a file name with the .read commnad. sqlite> .tables Cars Cars sqlite> DROP TABLE CARS; sqlite> .tables Cars sqlite> .read cars.sql
- 10. sqlite> .tables Cars Cars sqlite> SELECT * FROM Cars WHERE id=1; Id Name Cost ---------- ---------- ---------- 1 Audi 52642 Here we have executed a series of commands. We drop the table and read it from the cars.sql, that we have created previously. Resource file The sqlite3 tool has a resource file called .sqliterc. It is located in the home directory. If there is no such file, we can simply create it. We can place the meta commnads there or the regular SQL statements. However, we should avoid using SQL in the resource file. $ cat .sqliterc .mode column .header on .nullvalue NULL Here is a simple example of a resource file. It has three meta commands. With resource file, we don't have to execute meta commnads all over again, when we start the sqlite3 tool. They will be executed automatically at the start of the tool.
- 11. $ sqlite3 test.db -- Loading resources from /home/vronskij/.sqliterc SQLite version 3.5.9 Enter ".help" for instructions We have a message saying, that the tool loaded resources upon the beginning. Command line options The tool has several command line options. They mostly duplicate the meta commands. Note, that commnad line options overwrite the resource file meta commands. $ sqlite3 -version -- Loading resources from /home/vronskij/.sqliterc 3.5.9 We get the sqlite3 version. $ sqlite3 -html test.db -- Loading resources from /home/vronskij/.sqliterc SQLite version 3.5.9 Enter ".help" for instructions
- 12. sqlite> SELECT * FROM Cars LIMIT 2; <TR><TH>Id</TH><TH>Name</TH><TH>Cost</TH></TR> <TR><TD>1</TD> <TD>Audi</TD> <TD>52642</TD> </TR> <TR><TD>2</TD> <TD>Mercedes</TD> <TD>57127</TD> </TR> The -html option causes the results to be output as simple HTML tables In this part of the SQLite tutorial, we worked with the sqlite3 command line tool. We have described various meta commnads. We have shown, how to dump tables, read SQL from files; we described the sqlite's resource file.