SQLite

#
# Run this Tcl script to generate the sqlite.html file.
#
set rcsid {$Id: lang.tcl,v 1.70 2004/06/18 11:25:21 danielk1977 Exp $}
source common.tcl
header {Query Language Understood by SQLite}
puts {
<h2>SQL As Understood By SQLite</h2>

<p>The SQLite library understands most of the standard SQL
language.  But it does <a href="omitted.html">omit some features</a>

temporary tables.  These cannot be detached.  Attached databases 
are removed using the <a href="#detach">DETACH DATABASE</a> 
statement.</p>

<p>You can read from and write to an attached database and you
can modify the schema of the attached database.  This is a new
feature of SQLite version 3.0.  In SQLite 2.8, schema changes
to attached databases were not allowed.</p>

<p>You cannot create a new table with the same name as a table in 
an attached database, but you can attach a database which contains
tables whose names are duplicates of tables in the main database.  It is 
also permissible to attach the same database file multiple times.</p>

<p>Tables in an attached database can be referred to using the syntax 

of each CREATE INDEX statement is stored in the <b>sqlite_master</b>
or <b>sqlite_temp_master</b> table, depending on whether the table
being indexed is temporary.  Everytime the database is opened,
all CREATE INDEX statements
are read from the <b>sqlite_master</b> table and used to regenerate
SQLite's internal representation of the index layout.</p>


<p>Indexes are removed with the <a href="#dropindex">DROP INDEX</a> 
command.</p>
}


Section {CREATE TABLE} {createtable}

Syntax {sql-command} {
CREATE [TEMP | TEMPORARY] TABLE <table-name> (
  <column-def> [, <column-def>]*
  [, <constraint>]*
)
} {sql-command} {
CREATE [TEMP | TEMPORARY] TABLE [<database-name>.] <table-name> AS <select-statement>
} {column-def} {
<name> [<type>] [[CONSTRAINT <name>] <column-constraint>]*
} {type} {
<typename> |
<typename> ( <number> ) |
<typename> ( <number> , <number> )
} {column-constraint} {

<p>If the "TEMP" or "TEMPORARY" keyword occurs in between "CREATE"
and "TABLE" then the table that is created is only visible to the
process that opened the database and is automatically deleted when
the database is closed.  Any indices created on a temporary table
are also temporary.  Temporary tables and indices are stored in a
separate file distinct from the main database file.</p>

<p> If a <database-name> is specified, then the table is created in 
the named database. It is an error to specify both a <database-name>
and the TEMP keyword, unless the <database-name> is "temp". If no
database name is specified, and the TEMP keyword is not present,
the table is created in the main database.</p>

<p>The optional conflict-clause following each constraint
allows the specification of an alternative default
constraint conflict resolution algorithm for that constraint.
The default is abort ABORT.  Different constraints within the same
table may have different default conflict resolution algorithms.
If an COPY, INSERT, or UPDATE command specifies a different conflict

CREATE TABLE statement is synthesized and store in <b>sqlite_master</b>
in place of the original command.
The text of CREATE TEMPORARY TABLE statements are stored in the
<b>sqlite_temp_master</b> table.
</p>

<p>Tables are removed using the <a href="#droptable">DROP TABLE</a> 
statement.  </p>

}


Section {CREATE TRIGGER} createtrigger

Syntax {sql-statement} {
CREATE [TEMP | TEMPORARY] TRIGGER <trigger-name> [ BEFORE | AFTER ]

attached database.</p>
}


Section {CREATE VIEW} {createview}

Syntax {sql-command} {
CREATE [TEMP | TEMPORARY] VIEW [<database-name>.] <view-name> AS <select-statement>
}

puts {
<p>The CREATE VIEW command assigns a name to a pre-packaged 
<a href="#select">SELECT</a>
statement.  Once the view is created, it can be used in the FROM clause
of another SELECT in place of a table name.
</p>

<p>If the "TEMP" or "TEMPORARY" keyword occurs in between "CREATE"
and "TABLE" then the table that is created is only visible to the
process that opened the database and is automatically deleted when
the database is closed.</p>

<p> If a <database-name> is specified, then the view is created in 
the named database. It is an error to specify both a <database-name>
and the TEMP keyword, unless the <database-name> is "temp". If no
database name is specified, and the TEMP keyword is not present,
the table is created in the main database.</p>

<p>You cannot COPY, DELETE, INSERT or UPDATE a view.  Views are read-only 
in SQLite.  However, in many cases you can use a <a href="#trigger">
TRIGGER</a> on the view to accomplish the same thing.  Views are removed 
with the <a href="#dropview">DROP VIEW</a> 
command.  Non-temporary views cannot be created on tables in an attached 
database.</p>

command.</p>
}


Section {DROP TABLE} droptable

Syntax {sql-command} {
DROP TABLE [<database-name>.] <table-name>
}

puts {
<p>The DROP TABLE statement removes a table added with the <a href=
"#createtable">CREATE TABLE</a> statement.  The name specified is the
table name.  It is completely removed from the database schema and the 
disk file.  The table can not be recovered.  All indices associated 

puts {
<p>The ON CONFLICT clause is not a separate SQL command.  It is a
non-standard clause that can appear in many other SQL commands.
It is given its own section in this document because it is not
part of standard SQL and therefore might not be familiar.</p>

<p>The syntax for the ON CONFLICT clause is as shown above for

the CREATE TABLE and CREATE INDEX commands.  For the COPY, INSERT, and
UPDATE commands, the keywords "ON CONFLICT" are replaced by "OR", to make
the syntax seem more natural.  But the meaning of the clause is the same
either way.</p>

<p>The ON CONFLICT clause specifies an algorithm used to resolve
constraint conflicts.  There are five choices: ROLLBACK, ABORT,
FAIL, IGNORE, and REPLACE. The default algorithm is ABORT.  This
is what they mean:</p>

<dl>

by the default value for that column.  If the column has no default
value, then the ABORT algorithm is used.</p>

<p>When this conflict resolution strategy deletes rows in order to
statisfy a constraint, it does not invoke delete triggers on those
rows.  But that may change in a future release.</p>
























<p>The algorithm specified in the OR clause of a COPY, INSERT, or UPDATE
overrides any algorithm specified in a CREATE TABLE or CREATE INDEX.


If no algorithm is specified anywhere, the ABORT algorithm is used.</p>

}
# <p>For additional information, see 
# <a href="conflict.html">conflict.html</a>.</p>

<p>When an object (table, index, or trigger) is dropped from the 
database, it leaves behind empty space.  This makes the database 
file larger than it needs to be, but can speed up inserts.  In time 
inserts and deletes can leave the database file structure fragmented, 
which slows down disk access to the database contents.

The VACUUM command cleans
the main database by copying its contents to a temporary database file and 
reloading the original database file from the copy.  This eliminates 
free pages,  aligns table data to be contiguous, and otherwise cleans 
up the database file structure. It is not possible to perform the same
process on an attached database file.</p>

<p>This command will fail if there is an active transaction.  This 
command has no effect on an in-memory database.</p>
}


Section {SQLite keywords} keywords