Initialize a prepared statement
#include <qdb/qdb.h> int qdb_stmt_init( qdb_hdl_t *db, const char *sql, uint32_t len );
This function initializes a prepared (precompiled) SQL statement. A prepared statement is compiled once but can be executed multiple times. This function returns a statement ID for the prepared statement, which you must then pass in to qdb_stmt_exec().
QDB executes precompiled statements faster than uncompiled statements, so this approach can optimize your application's performance when executing frequently used statements.
You can free prepared statements using qdb_stmt_free(), although all such statements are freed when you call qdb_disconnect().
The following code sample shows how to compile, execute, and free an SQL statement:
int stmtid; qdb_binding_t qbind[2]; uint64_t msid, limit; const char *sql = "SELECT fid FROM library WHERE msid=?1 LIMIT ?2;"; stmtid = qdb_stmt_init(db, sql, strlen(sql)+1); if (stmtid == -1) { // Could not compile return -1; } msid = 1; limit = 10; QDB_SETBIND_INT(&qbind[0], 1, msid); QDB_SETBIND_INT(&qbind[1], 2, limit); if (qdb_stmt_exec(db, stmtid, qbind, 2) == -1) { // Could not execute return -1; } qdb_stmt_free(db, stmtid);
Note the +1 added to the length of the string returned by strlen() (which is used in the call to qdb_stmt_init()); this sends QDB the final NULL character required for a valid string.
QNX Neutrino
Safety: | |
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Interrupt handler | No |
Signal handler | No |
Thread | Yes |