C change sqlite prepare_stmt - c

Question

I have C code that creates different tables based on data being encountered in a separate operation. As a further complication, some of the data needs to be inserted into the same table as other data, and can be encountered in any order. As the data does have common indices, I am handling this using indices and UPSERT statements. Below is a simple example of the setup. The prepared statement doesn't seem to be updating as I am only getting partial insertions or none at all. I think this is related to some memory allocation on the statement?
// System includes
#include <stdlib.h>
#include <stdio.h>
// Local includes
#include <sqlite3.h>
// Function to create the insertion string for sqlite
char* insert_string(int flag)
{
if(flag==1)
{
return("INSERT INTO test(?, ?, ?, ?, ?) ON CONFLICT (a,b) DO UPDATE SET c=excluded.c, d=excluded.d");
}
else if(flag==2)
{
return("INSERT INTO test(?, ?, ?, ?, ?) ON CONFLICT (a,b) DO UPDATE SET e=excluded.e");
}
}
// Function to create tables based on an integer flag
void create_table(int flag, sqlite3* sqldb)
{
if(flag==1)
{
sqlite3_exec(sqldb, "CREATE TABLE IF NOT EXISTS test(a integer, b integer, c real, d real, e real)", NULL, NULL, NULL);
sqlite3_exec(sqldb, "CREATE UNIQUE INDEX IF NOT EXISTS sqldb_idx ON test(a,b)", NULL, NULL, NULL);
}
else if(flag==2)
{
sqlite3_exec(sqldb, "CREATE TABLE IF NOT EXISTS test(a integer, b integer, c real, d real, e real)", NULL, NULL, NULL);
sqlite3_exec(sqldb, "CREATE UNIQUE INDEX IF NOT EXISTS sqldb_idx ON test(a,b)", NULL, NULL, NULL);
}
}
int main()
{
// Initialize database
sqlite3 *sqldb;
int sql_rc;
sqlite3_stmt* sql_stmt;
sqlite3_open("test.db", &sqldb);
// Loop over some integer flags
for(int i=1; i<3; i++)
{
// Create the table and begin the transaction
create_table(i, sqldb);
sqlite3_exec(sqldb, "BEGIN TRANSACTION;", NULL, NULL, NULL);
// Prepare the insertion statement
sqlite3_prepare_v2(sqldb, insert_string(i), -1, &sql_stmt, NULL);
// Insert a different amount of data depending on the flag
sqlite3_bind_int(sql_stmt, 1, 1);
sqlite3_bind_int(sql_stmt, 2, 2);
if(i==1)
{
sqlite3_bind_double(sql_stmt,3,1.0);
sqlite3_bind_double(sql_stmt,4,2.0);
}
else if(i==2)
{
sqlite3_bind_double(sql_stmt,5,3.0);
}
sqlite3_step(sql_stmt);
sqlite3_reset(sql_stmt);
// End the transaction
sqlite3_exec(sqldb, "END TRANSACTION;", NULL, NULL, NULL);
}
// Finalize and close
sqlite3_finalize(sql_stmt);
sqlite3_close(sqldb);
}

Answer 1

The SQL you're attempting to compile isn't valid. This will fix it:
if(flag==1)
{
return("INSERT INTO test VALUES(?, ?, ?, ?, ?) ON CONFLICT (a,b) DO UPDATE SET c=excluded.c, d=excluded.d");
}
else if(flag==2)
{
return("INSERT INTO test VALUES(?, ?, ?, ?, ?) ON CONFLICT (a,b) DO UPDATE SET e=excluded.e");
}
Note the added VALUES in the SQL strings.
I'd also highly recommend checking all of the outputs of sqlite3_ calls, even in test code like this. Doing so will show that without the change here, the first call to sqlite3_prepare_v2 fails with a SQLITE_ERROR, showing a problem with the SQL itself.