[PyQt] QSql lastError() must be called BEFORE exec_() ??
Scott Frankel
frankel at circlesfx.com
Sat Sep 5 04:50:44 BST 2009
On Sep 4, 2009, at 1:23 PM, Mario Daniel Carugno wrote:
> Hi list, i'm coding my first PyQt4-Sql application, and i can't
> understand a strange behavior.
> I'll write a snippet of code with an erroneous Sql syntax, and i hope
> then to catch the error
> text and display it, in order to know what happened:
>
> query = QSqlQuery()
> query.prepare("insert inta table (name) values ('myname')") # note
> that 'inta' is an error
> query.exec_()
> if query.isActive() == False:
> print "ERRSQL " + str(g_session.db.lastError().text())
>
> And this do not work ! It is not displaying any text.
> To get it work, i must get the error string BEFORE the execution of
> the query !!
I believe you might be getting the correct lastError() string, but
from the previous time you ran your test.
> query = QSqlQuery()
> query.prepare("insert inta table (name) values ('myname')") # i made
> an erroneous sql
> query.exec_()
> errorstr = str(query.lastError().text())
> if query.isActive() == False:
> print "ERRSQL " + errorstr
>
> Is that behavior normal ?? How can PyQt get the error's text BEFORE
> executing the sql
> statement ?
I only use query.prepare() on rare occasions when I need to use
addBindValue() to achieve automagic character escaping. eg:
query.prepare("INSERT INTO foo ... ")
query.addBindValue(QtCore.QVariant(QtCore.QString("%s" % bar)))
err = query.exec_()
print "err: ", err
My typical handling of SQL calls is quite simple. I create a new
QSqlQuery object, pass it an SQL query string, then execute it. eg:
query = QtSql.QSqlQuery()
queryStr = "INSERT INTO foo ..."
query.exec_(queryStr)
print "lastError: ", query.lastError().text()
Hope this helps,
Scott
>
> This is very strange for me, don't you think ?
> It toke to me a long time to figure out how that works, because it
> don't seems to be
> logic. I mean, it's supposed that errors can be catched AFTER the
> execution of a statement,
> not BEFORE.
>
> Well, i just would like to hear why this works that way, if someone
> can explain it properly.
>
> Thanks
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