QPSQL: unable to create query

houssQt

Hi everyone,
I am trying to develop a desktop application that uses a postgresql database. i successfully connect to the server (postgresql 9.5) as the root "postgres", but when i try to execute a simple query as

SELECT * FROM information_schema.tables;

I get an error that say

QPSQL: unable to create query
ERROR: syntax error at the end of input
LINE1: EXECUTE

I stay ready to give any information that you will need.

houssQt

Hi again i guess i found the error in my code, first i had this

if(m_db.isOpen()) {
        QSqlQuery q(query,m_db);
        if(q.exec){
              // do somthing
        } else {
            executionError(q.lastError().driverText()+"\n"+
                           q.lastError().databaseText()+"\n"+
                           q.lastError().nativeErrorCode());
        }

the code above gave me the error, but when i use the QSqlDatabase object to directly exec the query it works just fine;

if(m_db.isOpen()) {
        auto q = m_db.exec(query);
        if(q.isActive()){
            // do something
        } else {
            executionError(q.lastError().driverText()+"\n"+
                           q.lastError().databaseText()+"\n"+
                           q.lastError().nativeErrorCode());
        }

i can't explain why, can anyone please explain why this behaviour ??.

SGaist

Hi and welcome to devnet,

It's all explained in the QSqlQuery constructor documentation.

If you pass a valid string, the query will be executed directly. So what is happening is that you are trying to run the query twice.