Note when the QSqlRecord field value is null. qsqlrecordnull

Note when the QSqlRecord field value is null. qsqlrecordnull

When the corresponding field value of QSqlRecord is null, QVariant returned by QSqlRecord: value is valid but null (equivalent to being constructed using QVariant (Type type ), so the corresponding type conversion can be successful (such as toInt )... After the conversion, the null result is converted into a specific value (such as 0), which may lead to a program error (-1 is usually used as the invalid value, 0 may lead to the normal process in the case of null ),Before using QSqlRecord: value, you must call QSqlRecord: isNull to determine the fields that may be null, or call QVariant: isNull to determine the fields.