QSQL error on insert into statement

[Cyrebo]

Hi, I'm working on a program where I get user input and insert that value to my database. At the moment, I'm getting the following error:

QSqlError(-1, "Unable to fetch row", "No query")

But I know thats its not my coding because when I try a select statement, it works fine with no problems. My INSERT INTO statement is as follows:

str = pLineEdit->text();
 QString qry = QString("INSERT INTO customer (name, phone_no, address, city) VALUES ('%%1%', NULL, NULL, NULL").arg(str);

str = pLineEdit->text();
 QString qry = QString("INSERT INTO customer (name, phone_no, address, city) VALUES ('%%1%', NULL, NULL, NULL").arg(str);

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Is my INSERT statement correct?