Qsql query to check whether integer is present or not in qt

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num is a integer and PassID also a integer
qry.prepare("SELECT * FROM ISSUEPASS WHERE PassID =num");
I need to select the row where the PassID matches
Iam getting error "unable to fetch row No query"

What I have tried:

qry.prepare("SELECT * FROM ISSUEPASS WHERE PassID =num");

Posted 21-Mar-18 20:34pm

Member 13740197

Updated 21-Mar-18 22:21pm

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Jochen Arndt · Accepted Answer · 2018-03-21T22:22:00

Solution 1

You have to create the query string passing num as parameter to a string formatting function. Because QSqlQuery::prepare() | Qt SQL 5.10[^] expects a QString argument, it can be be done in a single statement:

C++

qry.prepare(QString("SELECT * FROM ISSUEPASS WHERE PassID =%1").arg(num));

But SQL commands should never use created text strings to avoid SQL injections (here it would be OK because there is no text parameter). The preferred solution is using parametrised queries:

C++

qry.prepare("SELECT * FROM ISSUEPASS WHERE PassID =:passId");
qry.bindValue(":passId", num);

Posted 21-Mar-18 22:22pm

Jochen Arndt

Comments

Member 13740197 26-Mar-18 4:31am

It's working fine,but I had a problem when I am updating a parameter in the same row.

query.prepare("UPDATE ISSUEPASS SET INTIME =? WHERE PassID = :passId");
query.addBindValue(intime);
query.bindValue(":passId", num);
Here intime is QString variable,but Iam getting Sql error "Parameter Count mismatch"
Can you please tell me the solution.

Jochen Arndt 26-Mar-18 4:43am

You are mixing the two value binding methods:
named binding and positional binding.

That is not supported. Use one method:

query.prepare("UPDATE ISSUEPASS SET INTIME =:intime WHERE PassID = :passId");
query.bindValue(":intime", intime);
query.bindValue(":passId", num);

OR

query.prepare("UPDATE ISSUEPASS SET INTIME = ? WHERE PassID = ?);
query.addBindValue(intime);
query.addBindValue(num);

Member 13740197 26-Mar-18 5:33am

Thank you somuch for your answer