sqlite3_system_errno

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int sqlite3_system_errno  
(  
    sqlite3 *  
)  
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int sqlite3_system_errno (     sqlite3 * )

Remarks

CAPI3REF: The pre-update hook.

^These interfaces are only available if SQLite is compiled using the [SQLITE_ENABLE_PREUPDATE_HOOK] compile-time option.

^The [sqlite3_preupdate_hook()] interface registers a callback function that is invoked prior to each [INSERT], [UPDATE], and [DELETE] operation on a database table. ^At most one preupdate hook may be registered at a time on a single [database connection]; each call to [sqlite3_preupdate_hook()] overrides the previous setting. ^The preupdate hook is disabled by invoking [sqlite3_preupdate_hook()] with a NULL pointer as the second parameter. ^The third parameter to [sqlite3_preupdate_hook()] is passed through as the first parameter to callbacks.

^The preupdate hook only fires for changes to real database tables; the preupdate hook is not invoked for changes to [virtual tables] or to system tables like sqlite_master or sqlite_stat1.

^The second parameter to the preupdate callback is a pointer to the [database connection] that registered the preupdate hook. ^The third parameter to the preupdate callback is one of the constants [SQLITE_INSERT], [SQLITE_DELETE], or [SQLITE_UPDATE] to identify the kind of update operation that is about to occur. ^(The fourth parameter to the preupdate callback is the name of the database within the database connection that is being modified. This will be "main" for the main database or "temp" for TEMP tables or the name given after the AS keyword in the [ATTACH] statement for attached databases.)^ ^The fifth parameter to the preupdate callback is the name of the table that is being modified.

For an UPDATE or DELETE operation on a [rowid table], the sixth parameter passed to the preupdate callback is the initial [rowid] of the row being modified or deleted. For an INSERT operation on a rowid table, or any operation on a WITHOUT ROWID table, the value of the sixth parameter is undefined. For an INSERT or UPDATE on a rowid table the seventh parameter is the final rowid value of the row being inserted or updated. The value of the seventh parameter passed to the callback function is not defined for operations on WITHOUT ROWID tables, or for INSERT operations on rowid tables.

The [sqlite3_preupdate_old()], [sqlite3_preupdate_new()], [sqlite3_preupdate_count()], and [sqlite3_preupdate_depth()] interfaces provide additional information about a preupdate event. These routines may only be called from within a preupdate callback. Invoking any of these routines from outside of a preupdate callback or with a [database connection] pointer that is different from the one supplied to the preupdate callback results in undefined and probably undesirable behavior.

^The [sqlite3_preupdate_count(D)] interface returns the number of columns in the row that is being inserted, updated, or deleted.

^The [sqlite3_preupdate_old(D,N,P)] interface writes into P a pointer to a [protected sqlite3_value] that contains the value of the Nth column of the table row before it is updated. The N parameter must be between 0 and one less than the number of columns or the behavior will be undefined. This must only be used within SQLITE_UPDATE and SQLITE_DELETE preupdate callbacks; if it is used by an SQLITE_INSERT callback then the behavior is undefined. The [sqlite3_value] that P points to will be destroyed when the preupdate callback returns.

^The [sqlite3_preupdate_new(D,N,P)] interface writes into P a pointer to a [protected sqlite3_value] that contains the value of the Nth column of the table row after it is updated. The N parameter must be between 0 and one less than the number of columns or the behavior will be undefined. This must only be used within SQLITE_INSERT and SQLITE_UPDATE preupdate callbacks; if it is used by an SQLITE_DELETE callback then the behavior is undefined. The [sqlite3_value] that P points to will be destroyed when the preupdate callback returns.

^The [sqlite3_preupdate_depth(D)] interface returns 0 if the preupdate callback was invoked as a result of a direct insert, update, or delete operation; or 1 for inserts, updates, or deletes invoked by top-level triggers; or 2 for changes resulting from triggers called by top-level triggers; and so forth.

See also: [sqlite3_update_hook()] CAPI3REF: Low-level system error code

^Attempt to return the underlying operating system error code or error number that caused the most recent I/O error or failure to open a file. The return value is OS-dependent. For example, on unix systems, after [sqlite3_open_v2()] returns [SQLITE_CANTOPEN], this interface could be called to get back the underlying "errno" that caused the problem, such as ENOSPC, EAUTH, EISDIR, and so forth.