dbHasFeature

Purpose

Returns a 1 if the database supports the specified feature.

Format

ret = dbHasFeature(db_id, feature)

Parameters:

• db_id (scalar) – database connection index number.

• feature (scalar) –

  one of the following predefined scalars:

  Supported	Define	Description
  Yes	DB_TRANSACTIONS	Whether the driver supports SQL transactions.
  Yes	DB_QUERY_SIZE	Whether the database is capable of reporting the size of a query. Note that some databases do not support returning the size (i.e. number of rows returned) of a query. This can affect the performance when fetching results using functions like dbQueryFetchAllM() or dbQueryFetchAllSA()
  No	DB_BLOB	Whether the driver supports Binary Large Object fields.
  No	DB_UNICODE	Whether the driver supports Unicode strings if the database server does.
  Yes	DB_PREPARED_QUERIES	Whether the driver supports prepared query execution.
  Yes	DB_NAMED_PLACEHOLDERS	Whether the driver supports the use of named placeholders.
  Yes	DB_POSITIONAL_PLACEHOLDERS	Whether the driver supports the use of positional placeholders.
  Yes	DB_LAST_INSERT_ID	Whether the driver supports returning the Id of the last touched row.
  Yes	DB_BATCH_OPERATIONS	Whether the driver supports batched operations, see dbExecQueries().
  Yes	DB_SIMPLE_LOCKING	Whether the driver disallows a write lock on a table while other queries have a read lock on it.
  Yes	DB_LOW_PRECISION_NUMBERS	Whether the driver allows fetching numerical values with low precision.
  No	DB_EVENT_NOTIFICATIONS	Whether the driver supports database event notifications.
  Yes	DB_FINISH_QUERY	Whether the driver can do any low-level resource cleanup when dbQueryFinish() is called.
  No	DB_MULTIPLE_RESULT_SETS	Whether the driver can access multiple result sets returned from batched statements or stored procedures.
  No	DB_CANCEL_QUERY	Whether the driver allows cancelling a running query.

Returns:

ret (scalar) – 1 if the database supports the specified feature, or 0 if not.

Examples

// Set database connection index number
db_id = dbAddDatabase("MYSQL");

// Create empty query
qid = dbCreateQuery(db_id);

/*
** Use dbHasFeature to set up a
** conditional query
*/
if dbHasFeature(db_id, DB_NAMED_PLACEHOLDERS);
     dbQueryPrepare(qid, "SELECT * FROM GDP WHERE COUNTRY = :country");
     dbQueryBindValue(qid, ":country", "USA");
else;
     dbQueryPrepare(qid, "SELECT * FROM GDP WHERE COUNTRY = ?");
     dbQueryAddBindValue(qid, "USA");
endif;

dbQueryExecPrepared(qid);

Remarks

Note that some databases need to be opened with dbOpen() before this can be determined.