如何读取firebird数据库查询结果的大小？

Question

I am doing C interface with firebird databases. I did some query operations. I would like to know how to read the result size?

Below is the code. I have created and inserted some values into the table.I would like to read the size of the result.

#include <stdio.h>
#include "/Library/Frameworks/Firebird.framework/Versions/A/Headers/ibase.h"

static char *createTable="CREATE TABLE newex (Id int)"; //query for creating data table
static char *Insertvalues="INSERT INTO newex values (1)";//doing insertion into the   

//above created table

int SQLOpen(void)
{
    ISC_STATUS          status_vector[20];
    isc_tr_handle       transactionHandle = NULL; //transaction handle
    isc_db_handle       database = SQLGetDatabase();//database handle
    char                logInData [256], *dpb, *p;
    short               bufferLength;
    User_Credentials    credentials;

    sprintf(logInData, "%c%c%c%c%c%c%s%c%c%s",      isc_dpb_version1,
                                                    isc_dpb_num_buffers,
                                                    1,
                                                    90,
                                                    isc_dpb_user_name,
                                                    strlen("SYSDBA"),
                                                    "SYSDBA",
                                                    isc_dpb_password,
                                                    strlen("masterkey"),
                                                    "masterkey"); //passing user //credentials to connect to the database

    bufferLength = strlen(logInData);

    if (isc_attach_database(status_vector, strlen(DATABASE_PATH), DATABASE_PATH, &DatabaseHandle,bufferLength, logInData)) // connecting to database
    {
        SQLTestForErrors(status_vector);
        throw(ConnectionError, "");
    }
return 1;
}
char** SQLQuery(char *query, uint maxRows)
{
    isc_tr_handle   transactionHandle = NULL;
    isc_db_handle   database = SQLGetDatabase();
    short           bufferLength;
    char            dpb_buffer[256], *dpb, *p;
    ISC_STATUS      status_vector[20];


    isc_start_transaction(status_vector, &transactionHandle, 1, &database, 0, NULL);

    if (isc_dsql_execute_immediate(status_vector, &database, &transactionHandle, 0, query, 1, NULL)) //query operations 'create/insert'
    {
        SQLTestForErrors(status_vector);
        throw(QueryError, "");

    }
    isc_commit_transaction(status_vector, &transactionHandle);
   return testString;
}

int main()
{
    //struct Folder_table;
    e4c_using_context(E4C_TRUE)
    {

        SQLOpen();
        SQLQuery(createTable);
        SQLQuery(Insertvalues);
    }

}

Answer 1

You can't in advance: the result set is materialized while you are reading rows (using isc_fetch ): the final number of rows is not known until you have read all rows (at which point you can either have counted it yourself, or query it with an info request).

However I notice that you try to use isc_dsql_execute_immediate . You can only use isc_dsql_execute_immediate for ddl and for queries that produce one row (you need to prepare and execute for multiple rows).