Compiling the sqlite program from sources
The sqlite program is built automatically when you compile the sqlite library. Just get a copy of the source tree, run "configure" and then "make".
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" puts {The SQLite library includes a simple command-line utility named sqlite that allows the user to manually enter and execute SQL commands against an SQLite database. This document provides a brief introduction on how to use sqlite.
To start the sqlite program, just type "sqlite" followed by the name of an SQLite database. An SQLite database is really just a directory full of GDBM files, so the argument to the sqlite command should really be the name of a directory on your disk. If that directory did not previously contain an SQLite database, a new one is created for you automatically. The sqlite program will prompt you to enter SQL. Type in SQL statements (terminated by a semicolon, press "Enter" and the SQL will be executed. It's as simple as that!
For example, to create a new SQLite database named "ex1" with a single table named "tbl1", you might do this:
} proc Code {body} { puts {}
regsub -all {&} [string trim $body] {\&} body
regsub -all {>} $body {\>} body
regsub -all {<} $body {\<} body
regsub -all {\(\(\(} $body {} body
regsub -all {\)\)\)} $body {} body
puts $body
puts {(In the example above, and in all subsequent examples, the commands you type are shown with a green tint in an italic font and the responses from the computer are shown in black with a constant-width font.)
You can terminate the sqlite program by typing your systems End-Of-File character (usually a Control-D) or the interrupt character (usually a Control-C).
Make sure you type a semicolon at the end of each SQL command. The sqlite looks for a semicolon to know when your SQL command is complete. If you omit the semicolon, sqlite will give you a continuation prompt and wait for you to enter more text to be added to the current SQL command. This feature allows you to enter SQL commands that span multiple lines. For example:
} Code { sql> (((CREATE TABLE tbl2 ())) .... ((( f1 varchar(30) primary key,))) .... ((( f2 text,))) .... ((( f3 real))) .... ((();))) sql> } puts {If you exit sqlite and look at the contents of the directory "ex1" you'll see that it now contains two files: sqlite_master.tcl and tbl1.tbl. The tbl1.tbl file contains all the data for table "tbl1" in your database. The file sqlite_master.tbl is a special table found on all SQLite databases that records information about all other tables and indices. In general, an SQLite database will contain one "*.tbl" file for each table and index in your database, plus the extra "sqlite_master.tbl" file used to store the database schema.
You can execute "SELECT" statements against the special sqlite_master table just like any other table in an SQLite database. For example:
} Code { $ (((sqlite ex1))) Enter ".help" for instructions sql> (((select * from sqlite_master;))) type = table name = tbl1 tbl_name = tbl1 sql = create table tbl1(one varchar(10), two smallint) sql> } puts {But you cannot execute DROP TABLE, UPDATE, INSERT or DELETE against the sqlite_master table. At least not directly. The sqlite_master table is updated automatically as you create or drop tables and indices from the database, but you can not modify sqlite_master directly.
Most of the time, sqlite just reads lines of input and passes them on to the SQLite library for execution. But if an input line begins with a dot ("."), then that line is intercepted and interpreted by the sqlite program itself. These "dot commands" are typically used to change the output format of queries, or to execute certain command prepackaged query statements.
For a listing of the available dot commands, you can enter ".help" at any time. For example:
} Code { sql> (((.help))) .exit Exit this program .explain Set output mode suitable for EXPLAIN .header ON|OFF Turn display of headers on or off .help Show this message .indices TABLE Show names of all indices on TABLE .mode MODE Set mode to one of "line", "column", or "list" .output FILENAME Send output to FILENAME .output stdout Send output to the screen .schema ?TABLE? Show the CREATE statements .separator STRING Change separator string for "list" mode .tables List names all tables in the database .width NUM NUM ... Set column widths for "column" mode sql> } puts {The sqlite program is able to show the results of a query in three different formats: "line", "column", and "list". You can use the ".mode" dot command to switch between these three output formats.
In "line" mode (the default), each field in a record of the database is shown on a line by itself. Each line consists of the field name, an equal sign and the field data. Successive records are separated by a blank line. Here is an example of line mode output:
} Code { sql> (((.mode line))) sql> (((select * from tbl1;))) one = hello two = 10 one = goodbye two = 20 sql> } puts {In column mode, each record is shown on a separate line with the data aligned in columns. For example:
} Code { sql> (((.mode column))) sql> (((select * from tbl1;))) one two ---------- ---------- hello 10 goodbye 20 sql> } puts {By default, each column is 10 characters wide. Data that is too wide to fit in a column is truncated. You can adjust the column widths using the ".width" command. Like this:
} Code { sql> (((.width 12 6))) sql> (((select * from tbl1;))) one two ------------ ------ hello 10 goodbye 20 sql> } puts {The ".width" command in the example above set the width of the first column to 12 and the width of the second column to 6. All other column widths were unaltered. You can gives as many arguments to ".width" as necessary to specify the widths of as many columns as are in your query results.
The column labels that appear on the first two lines of output can be turned on and off using the ".header" dot command. In the examples above, the column labels are on. To turn them off you could do this:
} Code { sql> (((.header off))) sql> (((select * from tbl1;))) hello 10 goodbye 20 sql> } puts {The third output mode supported by sqlite is called "list". In list mode, each record of a query result is written on one line of output and each field within that record is separated by a specific separator string. The default separator is a pipe symbol ("|"). List mode is especially useful when you are going to send the output of a query to another program (such as AWK) for additional process.
} Code { sql> (((.mode list))) sql> (((select * from tbl1;))) hello|10 goodbye|20 sql> } puts {You can use the ".separator" dot command to change the separator for list mode. For example, to change the separator to a comma and a space, you could do this:
} Code { sql> (((.separator ", "))) sql> (((select * from tbl1;))) hello, 10 goodbye, 20 sql> } puts {By default, sqlite sends query results to standard output. You can change this using the ".output" command. Just put the name of an output file as an argument to the .output command and all subsequent query results will be written to that file. Use ".output stdout" to begin writing to standard output again. For example:
} Code { sql> (((.mode list))) sql> (((.separator |))) sql> (((.output test_file_1.txt))) sql> (((select * from tbl1;))) sql> (((.exit))) $ (((cat test_file_1.txt))) hello|10 goodbye|20 $ } puts {The sqlite program provides several convenience commands that are useful for looking at the schema of the database. There is nothing that these commands do that cannot be done by some other means. These commands are provided purely as a shortcut.
For example, to see a list of the tables in the database, you can enter ".tables".
} Code { sql> (((.tables))) tbl1 tbl2 sql> } puts {The ".tables" command is the same as setting list mode then executing the following query:
SELECT name FROM sqlite_master WHERE type='table' ORDER BY name;
In fact, if you look at the source code to the sqlite program (found in the source tree in the file src/shell.c) you'll find exactly the above query.
The ".indices" command works in a similar way to list all of the indices for a particular table. The ".indices" command takes a single argument which is the name of the table for which the indices are desired. Last, but not least, is the ".schema" command. With no arguments, the ".schema" command shows the original CREATE TABLE and CREATE INDEX statements that were used to build the current database. If you give the name of a table to ".schema", it shows the original CREATE statement used to make that table and all if its indices. We have:
} Code { sql> (((.schema))) create table tbl1(one varchar(10), two smallint) CREATE TABLE tbl2 ( f1 varchar(30) primary key, f2 text, f3 real ) sql> (((.schema tbl2))) CREATE TABLE tbl2 ( f1 varchar(30) primary key, f2 text, f3 real ) sql> } puts {The ".schema" command accomplishes the same thing as setting list mode, then entering the following query:
SELECT sql FROM sqlite_master ORDER BY tbl_name, type DESC, name
Of, if you give an argument to ".schema" because you only one the schema for a single table, the query looks like this:
SELECT sql FROM sqlite_master WHERE tbl_name LIKE '%s' ORDER BY type DESC, name
The %s in the query above is replaced by the argument to ".schema", of course.
The ".explain" dot command can be used to set the output mode to "column" and to set the column widths to values that are reasonable for looking at the output of an EXPLAIN command. The EXPLAIN command is an SQLite-specific command that is useful for debugging. If any regular SQL is prefaced by EXPLAIN, then the SQL command is parsed and analyzed but is not executed. Instead, the sequence of virtual machine instructions that would have been used to execute the SQL command are returned like a query result. For example:
} Code { sql> (((.explain))) sql> (((explain delete from tbl1 where two<20;))) addr opcode p1 p2 p3 ---- ------------ ----- ----- ------------------------------------- 0 ListOpen 0 0 1 Open 0 0 tbl1 2 Next 0 9 3 Field 0 1 4 Integer 20 0 5 Ge 0 2 6 Key 0 0 7 ListWrite 0 0 8 Goto 0 2 9 Noop 0 0 10 ListRewind 0 0 11 ListRead 0 14 12 Delete 0 0 13 Goto 0 11 14 ListClose 0 0 } puts {And finally, we mention the ".exit" command which causes the sqlite program to exit.
One way to use sqlite in a shell script is to use "echo" or "cat" to generate a sequence of commands in a file, then invoke sqlite while redirecting input from the generated command file. This works fine and is appropriate in many circumstances. But as an added convenience, sqlite allows a single SQL command to be entered on the command line as a second argument after the database name. When the sqlite program is launched with two arguments, the second argument is passed to the SQLite library for processing, the query results are printed on standard output in list mode, and the program exits. This mechanism is designed to make sqlite easy to use in conjunction with programs like "awk". For example:
} Code { $ (((sqlite ex1 'select * from tbl1' |))) > ((( awk '{printf "The sqlite program is built automatically when you compile the sqlite library. Just get a copy of the source tree, run "configure" and then "make".
} puts {
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