How to use DISTINCT while fetching data in sqlite in qt creator

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C++

I have table ISSUEPASS contains different rows with same PassID and mobile no.I want to get the PassID with the mobile no.I need to select only one row.I have tried below but Iam getting error "Unable fetch row,No query",Can you please provide me the solution.

QSqlQuery qry;
qry.prepare("SELECT DISTINCT(PassID) FROM ISSUEPASS WHERE mobno = '"+ui->lineEdit_mobno2->text()+"' ");

What I have tried:

QSqlQuery qry;
qry.prepare("SELECT DISTINCT(PassID) FROM ISSUEPASS WHERE mobno = '"+ui->lineEdit_mobno2->text()+"' ");