bestbarcoder.com

Executing SQL Queries in Java Produce barcode code 128 in Java Executing SQL Queries

Executing SQL Queries generate, create code 128 barcode none with java projects .NET Framework 3.0 query.exec_("DELETE FR ANSI/AIM Code 128 for Java OM calls WHERE id = 12"). After a query has exec uted we can check for errors by calling QSqlQuery.isActive(); if this returns False an error occurred and the error message is available as a QString by calling QSqlQuery.lastError().

text(). If we perform a query that may affect a number of rows, such as a DELETE or UPDATE whose WHERE clause might select more than one record, we can call QSqlQuery.numRowsAffected(); it returns -1 on error.

We can nd out whether the underlying database supports various features such as transactions and BLOBs (Binary Large OBjects) by accessing the driver and calling hasFeature(). For example:. driver = QSqlDatabase. barcode standards 128 for Java database().driver() if driver.

hasFeature(QSqlDriver.Transactions): print "Can commit and rollback". When we use QSqlQuery we can initiate a transaction by calling QSqlDatabase.database().transaction(), and then either QSqlDatabase.

database().commit() or QSqlDatabase.database().

rollback(). We will conclude our coverage of QSqlQuery by looking at how to use it to execute SELECT statements, and how to iterate over the resultant records..

DATETIME_FORMAT = "yyy tomcat barcode standards 128 y-MM-dd hh:mm" ID, CALLER, STARTTIME, ENDTIME, TOPIC, OUTCOMEID = range(6) query.exec_("SELECT id, caller, starttime, endtime, topic, " "outcomeid FROM calls ORDER by starttime") while query.next(): id = query.

value(ID).toInt()[0] caller = unicode(query.value(CALLER).

toString()) starttime = unicode(query.value(STARTTIME).toDateTime() \ .

toString(DATETIME_FORMAT)) endtime = unicode(query.value(ENDTIME).toDateTime() \ .

toString(DATETIME_FORMAT)) topic = unicode(query.value(TOPIC).toString()) outcomeid = query.

value(OUTCOMEID).toInt()[0] subquery = QSqlQuery("SELECT name FROM outcomes " "WHERE id = %d" % outcomeid) outcome = "invalid foreign key" if subquery.next(): outcome = unicode(subquery.

value(0).toString()) print "%02d: %s %s - %s %s [%s]" % (id, caller, starttime, endtime, topic, outcome). When we execute a SELE CT statement, we can iterate over the result set using methods such as QSqlQuery.next(), QSqlQuery.previous(), and QSqlQuery.

seek(). Immediately after a successful SELECT, isActive() will return True but the inter-. 15. Databases Table 15.1 Selected QSqlQuery Methods Syntax q.addBindValue( tomcat code 128b v) q.bindValue(p, v) q.

boundValue(p) q.driver(). Description q.exec_(s) q.first() q awt code-128c .

isActive() q.isValid(). Adds QVariant v as the next variable when using positional value binding in QSqlQuery q Sets QVariant v as the value for the string p place holder when using place holder value binding in QSqlQuery q Returns the QVariant value for the string p place holder in QSqlQuery q Returns the QSqlDriver associated with QSqlQuery q. The QSqlDriver class provides hasFeature() to report which features the underlying database supports. Executes the SQL query in string s on QSqlQuery q Navigates to the rst record in QSqlQuery q s result set after a SELECT query has been executed Returns True if the query is active for example, after executing a SELECT query Returns True if the query is positioned on a valid record; after a SELECT query this will be True only if isActive() is True and a record has been navigated to Navigates to the last record in QSqlQuery q s result set after a SELECT query has been executed Returns a QSqlError object; this provides an errorString() method Navigates to the next record in QSqlQuery q s result set after a SELECT query has been executed.

This is the only method needed to iterate forward over a result set. Returns the number of rows affected by the SQL query just executed, providing it was not a SELECT, and providing the underlying database supports this feature Prepares the query in string s ready for q to execute it Navigates to the previous record in QSqlQuery q s result set after a SELECT query has been executed Returns a QSqlRecord object containing QSqlQuery q s current record, if any; using QSqlQuery.value() with a eld index argument is usually more convenient Returns the number of rows in the SELECT result set, or -1 if a SELECT was not executed or if the underlying database does not support this feature Returns the QVariant value for eld index int i in the current record, if there is one.

q.last() q.lastError() code-128b for Java q.

next(). q.numRowsAffected() q. prepare(s) q.

previous() q.record(). q.size(). q.value(i).
Copyright © bestbarcoder.com . All rights reserved.