What does statement "insert" in SQLite return in case of success?
I always believed that it should be SQLITE_DONE, but recently in my logs I found out the following string:
sqlite3_step error: 'not an error'
And here is the code that logs the mentioned string:
prepareStatement(addTranslationStmt2, "INSERT INTO translations(lang1_wordid, lang2_wordid) VALUES(?, ?)");
if (!addTranslationStmt2) return -2;
sqlite3_bind_int(addTranslationStmt2, 1, word_id);
sqlite3_bind_int(addTranslationStmt2, 2, translation_id);
if(sqlite3_step(addTranslationStmt2) != SQLITE_DONE)
{
NSLog(#"sqlite3_step error: '%s'", sqlite3_errmsg(database));
sqlite3_reset(addTranslationStmt2);
return -1;
}
sqlite3_reset(addTranslationStmt2);
I am wondering, why does it work in most cases.
Should I change SQLITE_DONE in my code to SQLITE_OK?
Thanks.
SQLITE_DONE
http://www.sqlite.org/c3ref/step.html
You could also try printing out the error code to find out what the problem is.
In cases like these, I like to look at code samples. Here are some good ones:
http://sqlite.phxsoftware.com/forums/p/76/6659.aspx
The SQLite Result Codes Reference lists SQLITE_OK as indicating a successful result. It is also the first error code, having an error code of 0, making it the canonical result (i.e. the result I would expect on a successful operation).
You should put a breakpoint or print statement in your code to find out if it really is returning zero, and check your data to make sure you're getting the result you expect. If that all checks out, I would change your condition to check for SQLITE_OK.
The details of the behavior of the sqlite3_step() interface depend on whether the statement was prepared using the newer "v2" interface sqlite3_prepare_v2() and sqlite3_prepare16_v2() or the older legacy interface sqlite3_prepare() and sqlite3_prepare16().
In the legacy interface, the return value will be either SQLITE_BUSY, SQLITE_DONE, SQLITE_ROW, SQLITE_ERROR, or SQLITE_MISUSE. With the "v2" interface, any of the other result codes or extended result codes might be returned as well.
Switching from "Debug" configuration to "Release" resolved the issue for me.
Related
I am trying to build some smart error messages using the #app.errorhandler (500) feature. For example, my route includes an INSERT command to the database:
if request.method == "POST":
userID = int(request.form.get("userID"))
topicID = int(request.form.get("topicID"))
db.execute("BEGIN TRANSACTION")
db.execute("INSERT INTO UserToTopic (userID,topicID) VALUES (?,?)", userID, topicID)
db.execute("COMMIT")
If that transaction violates a constraint, such as UNIQUE or FOREIGN_KEY, I want to catch the error and display a user-friendly message. To do this, I'm using the Flask #app.errorhandler as follows:
#app.errorhandler(500)
def internal_error(error):
db.execute("ROLLBACK")
return render_template('500.html'), 500
The "ROLLBACK" command works fine if I'm in the middle of a database transaction. But sometimes the 500 error is not related to the db, and in those cases the ROLLBACK statement itself causes an error, because you can't rollback a transaction that never started. So I'm looking for a method that returns a Boolean value that would be true if a db transaction is under way, and false if not, so I can use it to make the ROLLBACK conditional. The only one I can find in the SQLite3 documentation is for a C interface, and I can't get it to work with my Python code. Any suggestions?
I know that if I'm careful enough with my forms and routes, I can prevent 99% of potential violations of db rules. But I would still like a smart error catcher to protect me for the other 1%.
I don't know how transaction works in sqlite but what you are trying to do, you can achieve it by try/except statements
use try/except within the function
try:
db.execute("ROLLBACK")
except:
pass
return render_template('500.html'), 500
Use try/except when inserting data.
from flask import abort
try:
userID = int(request.form.get("userID"))
[...]
except:
db.rollback()
abort(500)
I am not familiar with sqlite errors, if you know what specific error occurs except for that specific error.
I am using this query to get some statistics from our DB
SELECT DateTimePart("yyyy", c.RedeemedDate) AS RedeemedInYear,
DateTimePart("m", c.RedeemedDate) AS RedeemedInMonth,
AVG(c.RedPriceStoreSummary ?? c.WhitePriceStoreSummary) AS AverageBasketValue
FROM c
WHERE c.IsRedeemed = true
AND c.Brand = 'xxx'
AND c.RedeemedDate != null
AND DateTimePart("yyyy", c.RedeemedDate) = DateTimePart("yyyy", GetCurrentDateTime())
GROUP BY DateTimePart("m", c.RedeemedDate),
DateTimePart("yyyy", c.RedeemedDate)
The problem is that query crashes with the following error if there are no results
Cannot read property 'create' of undefined
If I force the query to where it gets results then everything works fine but I dont want the query to crash if there are no results I want an empty result set.
Am I missing something here?
You need to trap queries in a try block and catch if it returns a 404. This is a hold over in behavior from the previous SDK. Alternatively you can use the stream variant of these SDK functions which will not throw exceptions when data is not found, however you still want to check the http response code and you'll also need to manually deserialize the data.
I was trying to make a website using perl dancer, below is my code. It seems to be correct but the page keeps loading and never enters the values in the database. When I cancel the page I get an error stating "request to POST /appform crashed: Can't call method "execute" on an undefined value". I can't figured out whats wrong in the code. If you have any other code please mention.
I am using SQLite for database.
There is a database campus.dband I am inserting the value in student table.
post '/appform' => sub {
my $q = CGI ->new;
my $name = $q->param ("firstname");
my $password = $q->param("password");
my $mobile_no = $q->param("mobile");
my $gender = $q->param("gender");
my $email = $q->param("email");
my $address = $q->param("address");
my $sslc = $q->param("SSLC");
my $hsc = $q->param("HSC");
my $cgpa = $q->param("cgpa");
my $languages = $q->param("lang");
my $internships = $q->param("intern");
my $preferred_loc = $q->param("country");
my $sql = "insert into student(name,mobile_no,gender,email,address,sslc,hsc,cgpa,languages,internships,preferred_loc,password,applied_job,company_applied) values ('?','?','?','?','?','?','?','?','?','?','?','?','?','?');";
my $sth = database->prepare($sql);
$sth->execute($name,$mobile_no,$gender,$email,$address,$sslc,$hsc,$cgpa,$languages,$internships,$preferred_loc,$password) or die $sth->errstr;
#$sth->execute();
$sth-> finish;
set_flash('New entry posted!');
redirect '/';
};
You're using the database keyword to get a database handle. I'm guessing that's coming from Dancer2::Plugin::Database (it would be useful if you could include information like this in your question).
The error says that you're calling execute() on an undefined value. You're calling execute() on the variable $sth. So $sth is undefined. You get $sth by calling prepare() on the database handle returned from database(). So it looks like the prepare() call is failing. You should check the return value from that call and throw an error if it fails.
The most common reason for prepare() to fail is that you're trying to compile an SQL statement that contains an error. I can't see any obvious error in your SQL, but it's worth checking it by running it manually against your database.
I see you're using bind params in your SQL statement. That's a great idea, but please note that you don't need to quote the question marks in your SQL - the database driver will handle that for you. I don't think that's what is causing your problem though.
I also see that you're using CGI.pm inside your Dancer app to get the request parameters. To be honest, I'm slightly surprised that it works - but it's a terrible idea. Dancer has its own keywords that will give you this information. Look at query_parameters(), body_parameters() and route_parameters() in the Dancer documentation.
In addition to the points made already, that your DBI prepare() call is probably failing (add error-checking to see why, e.g. my $sth = database->prepare('...') or die "DB error: " . database->errstr) and that you're using CGI.pm within a Dancer app (... don't do that, I'm surprised it would work at all - look at the Dancer documentation for how to access the params your app was sent), look also at the quick_insert convenience method provided by Dancer::Plugin::Database / Dancer2::Plugin::Database so that you don't have to write that SQL INSERT statement at all.
We are using the tSQLt framework and have the below code in the test.
IF #count>0
EXEC tsqlt.fail;
else EXEC tSQLt.AssertEquals 1,1;
I am interested to know how we can display a custom test success or failure message when this test gets executed?
tSQLt.fail takes up to 10 parameters that all get concatenated into a custom failure message.
You also do not need the call to tSQLt.AssertEquals as it, in your case, literally does nothing.
BTW, asserting a count is in almost all cases a bad idea, as it does not really tell you anything about the result. If you get the correct count back, you could still have wrong data. And if you get the incorrect count, you don't have any additional info on what went wrong.
Have a look at tSQLt.AssertEqualsTable or tSQLt.AssertEmptyTable instead.
Here is my code, there doesn't seem to be anything wrong:
QSqlDatabase db=QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName("thedata.sqlite");
db.open();
QSqlQuery query;
query.prepare("SELECT lastname FROM people where firstname='?' ");
query.bindValue(0, lineEdit->text());
bool x = query.exec();
if(x){
lineEdit_2->setText(query.value(0).toString());
}
else {
QSqlError err;
err = query.lastError();
QMessageBox::about(this,"error",err.text() );
}
When the program is working always it gives the error parameter count mismatch I'm using qt 4.8 and its own headers for using sqlite.
I would be very thankful for any advice, though I searched in google i see many posts in this issue but nothing helped me.
Thank you.
You're prepared statement is wrong, it should be:
quary.prepare("SELECT lastname FROM people where firstname=?");
Notice that there are no single quotes (') around the placeholder. If you put the quotes, it gets passed as a literal to the database, leaving you with a parameter-less query and code that passes too many parameters.
(Changing that variable name to query would be a nice touch too.)
Also you need to check the return value if QSqlQuery::prepare, and print out/display the error message you're getting from that if it fails – otherwise QSqlQuery::exec resets the current error and you'll get a pretty meaningless error message if there was a problem parsing the prepared statement.
if(x){
lineEdit_2->setText(quary.value(0).toString());
}
This is incorrect too. The you need to call (and check the return value of) query.next() to position the result set to the first row returned (if there is one). You can't use .value(X) before you've called .next().