These routines open an SQLite database file as specified by the filename
argument. The filename argument is interpreted as UTF-8 for sqlite3_open() and
sqlite3_open_v2() and as UTF-16 in the native byte order for sqlite3_open16().
A database connection handle is usually returned in *ppDb, even if an error
occurs. The only exception is that if SQLite is unable to allocate memory to
hold the sqlite3 object, a NULL will be written into *ppDb instead of a
pointer to the sqlite3 object. If the database is opened (and/or created)
successfully, then SQLITE_OK is returned. Otherwise an error code is returned.
The sqlite3_errmsg() or sqlite3_errmsg16() routines can be used to obtain an
English language description of the error following a failure of any of the
sqlite3_open() routines.
The default encoding will be UTF-8 for databases created using
sqlite3_open() or sqlite3_open_v2(). The default encoding for databases
created using sqlite3_open16() will be UTF-16 in the native byte order.
Whether or not an error occurs when it is opened, resources
associated with the database connection handle should be released by passing
it to sqlite3_close() when it is no longer required.
The sqlite3_open_v2() interface works like sqlite3_open() except
that it accepts two additional parameters for additional control over the
new database connection. The flags parameter to sqlite3_open_v2() can take
one of the following three values, optionally combined with the
SQLITE_OPEN_NOMUTEX, SQLITE_OPEN_FULLMUTEX, SQLITE_OPEN_SHAREDCACHE,
SQLITE_OPEN_PRIVATECACHE, and/or SQLITE_OPEN_URI flags:
- SQLITE_OPEN_READONLY
- The database is opened in read-only mode. If the database does not already
exist, an error is returned.
- SQLITE_OPEN_READWRITE
- The database is opened for reading and writing if possible, or reading
only if the file is write protected by the operating system. In either
case the database must already exist, otherwise an error is returned.
- SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE
- The database is opened for reading and writing, and is created if it does
not already exist. This is the behavior that is always used for
sqlite3_open() and sqlite3_open16().
If the 3rd parameter to sqlite3_open_v2() is not one of the
combinations shown above optionally combined with other SQLITE_OPEN_* bits
then the behavior is undefined.
If the SQLITE_OPEN_NOMUTEX flag is set, then the database
connection opens in the multi-thread threading mode as long as the
single-thread mode has not been set at compile-time or start-time. If the
SQLITE_OPEN_FULLMUTEX flag is set then the database connection opens in the
serialized threading mode unless single-thread was previously selected at
compile-time or start-time. The SQLITE_OPEN_SHAREDCACHE flag causes the
database connection to be eligible to use shared cache mode, regardless of
whether or not shared cache is enabled using sqlite3_enable_shared_cache().
The SQLITE_OPEN_PRIVATECACHE flag causes the database connection to not
participate in shared cache mode even if it is enabled.
The fourth parameter to sqlite3_open_v2() is the name of the
sqlite3_vfs object that defines the operating system interface that the new
database connection should use. If the fourth parameter is a NULL pointer
then the default sqlite3_vfs object is used.
If the filename is ":memory:", then a private, temporary
in-memory database is created for the connection. This in-memory database
will vanish when the database connection is closed. Future versions of
SQLite might make use of additional special filenames that begin with the
":" character. It is recommended that when a database filename
actually does begin with a ":" character you should prefix the
filename with a pathname such as "./" to avoid ambiguity.
If the filename is an empty string, then a private, temporary
on-disk database will be created. This private database will be
automatically deleted as soon as the database connection is closed.
If URI filename interpretation is enabled, and the filename argument begins with
"file:", then the filename is interpreted as a URI. URI filename
interpretation is enabled if the SQLITE_OPEN_URI flag is set in the third
argument to sqlite3_open_v2(), or if it has been enabled globally using the
SQLITE_CONFIG_URI option with the sqlite3_config() method or by the
SQLITE_USE_URI compile-time option. URI filename interpretation is turned off
by default, but future releases of SQLite might enable URI filename
interpretation by default. See "URI filenames" for additional
information.
URI filenames are parsed according to RFC 3986. If the URI
contains an authority, then it must be either an empty string or the string
"localhost". If the authority is not an empty string or
"localhost", an error is returned to the caller. The fragment
component of a URI, if present, is ignored.
SQLite uses the path component of the URI as the name of the disk
file which contains the database. If the path begins with a '/' character,
then it is interpreted as an absolute path. If the path does not begin with
a '/' (meaning that the authority section is omitted from the URI) then the
path is interpreted as a relative path. On windows, the first component of
an absolute path is a drive specification (e.g. "C:").
The query component of a URI may contain parameters that are
interpreted either by SQLite itself, or by a custom VFS implementation.
SQLite and its built-in VFSes interpret the following query parameters:
- vfs: The "vfs" parameter may be used to specify the name
of a VFS object that provides the operating system interface that should
be used to access the database file on disk. If this option is set to an
empty string the default VFS object is used. Specifying an unknown VFS is
an error. If sqlite3_open_v2() is used and the vfs option is present, then
the VFS specified by the option takes precedence over the value passed as
the fourth parameter to sqlite3_open_v2().
- mode: The mode parameter may be set to either "ro",
"rw", "rwc", or "memory". Attempting to set
it to any other value is an error . If "ro" is specified, then
the database is opened for read-only access, just as if the
SQLITE_OPEN_READONLY flag had been set in the third argument to
sqlite3_open_v2(). If the mode option is set to "rw", then the
database is opened for read-write (but not create) access, as if
SQLITE_OPEN_READWRITE (but not SQLITE_OPEN_CREATE) had been set. Value
"rwc" is equivalent to setting both SQLITE_OPEN_READWRITE and
SQLITE_OPEN_CREATE. If the mode option is set to "memory" then a
pure in-memory database that never reads or writes from disk is used. It
is an error to specify a value for the mode parameter that is less
restrictive than that specified by the flags passed in the third parameter
to sqlite3_open_v2().
- cache: The cache parameter may be set to either "shared"
or "private". Setting it to "shared" is equivalent to
setting the SQLITE_OPEN_SHAREDCACHE bit in the flags argument passed to
sqlite3_open_v2(). Setting the cache parameter to "private" is
equivalent to setting the SQLITE_OPEN_PRIVATECACHE bit. If
sqlite3_open_v2() is used and the "cache" parameter is present
in a URI filename, its value overrides any behavior requested by setting
SQLITE_OPEN_PRIVATECACHE or SQLITE_OPEN_SHAREDCACHE flag.
- psow: The psow parameter indicates whether or not the powersafe
overwrite property does or does not apply to the storage media on which
the database file resides.
- nolock: The nolock parameter is a boolean query parameter which if
set disables file locking in rollback journal modes. This is useful for
accessing a database on a filesystem that does not support locking.
Caution: Database corruption might result if two or more processes write
to the same database and any one of those processes uses nolock=1.
- immutable: The immutable parameter is a boolean query parameter
that indicates that the database file is stored on read-only media. When
immutable is set, SQLite assumes that the database file cannot be changed,
even by a process with higher privilege, and so the database is opened
read-only and all locking and change detection is disabled. Caution:
Setting the immutable property on a database file that does in fact change
can result in incorrect query results and/or SQLITE_CORRUPT errors.
Specifying an unknown parameter in the query component of a URI is
not an error. Future versions of SQLite might understand additional query
parameters. See "query parameters with special meaning to SQLite"
for additional information.
<table border="1" align=center cellpadding=5>
<tr><th> URI filenames <th> Results <tr><td>
file:data.db <td> Open the file "data.db" in the current
directory. <tr><td> file:/home/fred/data.db<br>
file:///home/fred/data.db <br> file://localhost/home/fred/data.db
<br> <td> Open the database file "/home/fred/data.db".
<tr><td> file://darkstar/home/fred/data.db <td> An error.
"darkstar" is not a recognized authority. <tr><td
style="white-space:nowrap">
file:///C:/Documents%20and%20Settings/fred/Desktop/data.db <td> Windows
only: Open the file "data.db" on fred's desktop on drive C:. Note
that the %20 escaping in this example is not strictly necessary - space
characters can be used literally in URI filenames. <tr><td>
file:data.db?mode=ro&cache=private <td> Open file
"data.db" in the current directory for read-only access. Regardless
of whether or not shared-cache mode is enabled by default, use a private
cache. <tr><td> file:/home/fred/data.db?vfs=unix-dotfile
<td> Open file "/home/fred/data.db". Use the special VFS
"unix-dotfile" that uses dot-files in place of posix advisory
locking. <tr><td> file:data.db?mode=readonly <td> An error.
"readonly" is not a valid option for the "mode" parameter.
</table>
URI hexadecimal escape sequences (%HH) are supported within the
path and query components of a URI. A hexadecimal escape sequence consists
of a percent sign - "%" - followed by exactly two hexadecimal
digits specifying an octet value. Before the path or query components of a
URI filename are interpreted, they are encoded using UTF-8 and all
hexadecimal escape sequences replaced by a single byte containing the
corresponding octet. If this process generates an invalid UTF-8 encoding,
the results are undefined.
Note to Windows users: The encoding used for the filename
argument of sqlite3_open() and sqlite3_open_v2() must be UTF-8, not whatever
codepage is currently defined. Filenames containing international characters
must be converted to UTF-8 prior to passing them into sqlite3_open() or
sqlite3_open_v2().
Note to Windows Runtime users: The temporary directory must
be set prior to calling sqlite3_open() or sqlite3_open_v2(). Otherwise,
various features that require the use of temporary files may fail.