SQLite UPDATE fails to overwrite existing value - c++

Question

I have the following problem that has me stumped. As a note to keep in mind, I am using a precompiled sqlite3.dll rather than Qt's built-in SQLite support.
Table creation code:
CREATE TABLE STUDY(
Name NOT NULL,
UserName NOT NULL REFERENCES USERS(UserName),
Description DEFAULT NULL,
PathToOsirixDB DEFAULT NULL,
PRIMARY KEY(Name, UserName)
)
The following C++ code fails to update the value in column PathToOsirixDB if it already contains a value.
It fails silently, with no error returned. That would imply that no rows are matched in the UPDATE. However, if I take the same UPDATE with valid entries for user and study to match a row and run it via either the SQLite Manager Firefox plugin, or the command line tool, it works properly.
void CStudyDatabase::SetOsirixDBForStudy(const QString user, const QString study, const QString path)
{
if (mp_db)
{
int before = sqlite3_total_changes(mp_db);
QString insert = QString("UPDATE STUDY SET PathToOsirixDB = '%1' WHERE Name = '%2' AND UserName = '%3'").arg(path, study, user);
if (!InsertData(insert))
{
int after = sqlite3_total_changes(mp_db);
if (after - before >= 1)
{
SetOsirixDB(path.toAscii().data());
emit ReturnOsirixDB(osirix_db);
}
else
{
emit DatabaseError(QString("Failed to update the target path."));
}
}
}
}
And for Insert Data
int CStudyDatabase::InsertData(const QString insert)
{
char *err_msg = 0;
int rc = sqlite3_exec(mp_db,
insert.toStdString().c_str(),
NULL,
this,
&err_msg);
if (rc)
SignalDatabaseError(&err_msg);
return rc;
}
Any insights are appreciated. Thank you.
UPDATE: added the following code to SetOsiriXDBForStudy to see if we actually find a row to update:
osirix_db = QString("");
QString query = QString("SELECT PathToOsirixDB FROM STUDY WHERE Name = '%1' AND UserName = '%2'").arg(study, user);
int rc = 0;
char *err_msg = 0;
rc = sqlite3_exec(mp_db,
query.toStdString().c_str(),
&OsirixDBCallback,
this,
&err_msg);
if (rc)
SignalDatabaseError(&err_msg);
if (!(QString(osirix_db).isEmpty()))
studyrowfound = true;
In this case, it leaves osirix_db as an empty string.
But, if I execute this function:
void CStudyDatabase::QueryOsirixDB(const QString user, const QString study)
{
int rc = 0;
char *err_msg = 0;
// we query the OrisixDB via the callback and then emit the signal if all went well
QString query = QString("SELECT PathToOsirixDB FROM STUDY WHERE Name = '%1' AND UserName = '%2'").arg(study, user);
rc = sqlite3_exec(mp_db,
query.toStdString().c_str(),
&OsirixDBCallback,
this,
&err_msg);
if (rc)
SignalDatabaseError(&err_msg);
if (QString(osirix_db).isEmpty())
emit NeedToSetOsirixDB(user, study, QString());
else
emit ReturnOsirixDB(osirix_db);
}
Then it does correctly retrieve the expected value into osirix_db.
Last update: found the problem. It was leading spaces on user and study. Had been staring at the same debugger statements for too long and glossed over the extra spaces. The failing SELECT was a big clue that there was something wrong in the construction of the SQL.

Answer 1

There were leading spaces on user and study. Had been staring at the same debugger statements for too long and glossed over the extra spaces. The failing SELECT was a big clue that there was something wrong in the construction of the SQL.