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()ordbQueryFetchAllSA()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);