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QSqlQuery(3qt)									   QSqlQuery(3qt)

NAME
       QSqlQuery - Means of executing and manipulating SQL statements

SYNOPSIS
       #include <qsqlquery.h>

       Inherited by QSqlCursor.

   Public Members
       QSqlQuery ( QSqlResult * r )
       QSqlQuery ( const QString & query = QString::null, QSqlDatabase * db = 0 )
       explicit QSqlQuery ( QSqlDatabase * db )
       QSqlQuery ( const QSqlQuery & other )
       QSqlQuery & operator= ( const QSqlQuery & other )
       virtual ~QSqlQuery ()
       bool isValid () const
       bool isActive () const
       bool isNull ( int field ) const
       int at () const
       QString lastQuery () const
       int numRowsAffected () const
       QSqlError lastError () const
       bool isSelect () const
       int size () const
       const QSqlDriver * driver () const
       const QSqlResult * result () const
       bool isForwardOnly () const
       void setForwardOnly ( bool forward )
       virtual bool exec ( const QString & query )
       virtual QVariant value ( int i ) const
       virtual bool seek ( int i, bool relative = FALSE )
       virtual bool next ()
       virtual bool prev ()
       virtual bool first ()
       virtual bool last ()
       bool exec ()
       bool prepare ( const QString & query )
       void bindValue ( const QString & placeholder, const QVariant & val )
       void bindValue ( int pos, const QVariant & val )
       void addBindValue ( const QVariant & val )
       void bindValue ( const QString & placeholder, const QVariant & val, QSql::ParameterType
	   type )
       void bindValue ( int pos, const QVariant & val, QSql::ParameterType type )
       void addBindValue ( const QVariant & val, QSql::ParameterType type )
       QVariant boundValue ( const QString & placeholder ) const
       QVariant boundValue ( int pos ) const
       QMap<QString, QVariant> boundValues () const
       QString executedQuery () const

   Protected Members
       virtual void beforeSeek ()
       virtual void afterSeek ()

DESCRIPTION
       The QSqlQuery class provides a means of executing and manipulating SQL statements.

       QSqlQuery encapsulates the functionality involved in creating, navigating and retrieving
       data from SQL queries which are executed on a QSqlDatabase. It can be used to execute DML
       (data manipulation language) statements, e.g. SELECT, INSERT, UPDATE and DELETE, and also
       DDL (data definition language) statements, e.g. CREATE TABLE. It can also be used to
       execute database-specific commands which are not standard SQL (e.g. SET DATESTYLE=ISO for
       PostgreSQL).

       Successfully executed SQL statements set the query's state to active (isActive() returns
       TRUE); otherwise the query's state is set to inactive. In either case, when executing a
       new SQL statement, the query is positioned on an invalid record; an active query must be
       navigated to a valid record (so that isValid() returns TRUE) before values can be
       retrieved.

       Navigating records is performed with the following functions:

       next()

       prev()

       first()

       last()

       seek(int)

       These functions allow the programmer to move forward, backward or arbitrarily through the
       records returned by the query. If you only need to move forward through the results, e.g.
       using next() or using seek() with a positive offset, you can use setForwardOnly() and save
       a significant amount of memory overhead. Once an active query is positioned on a valid
       record, data can be retrieved using value(). All data is transferred from the SQL backend
       using QVariants.

       For example:

	   QSqlQuery query( "SELECT name FROM customer" );
	   while ( query.next() ) {
	       QString name = query.value(0).toString();
	       doSomething( name );
	   }

       To access the data returned by a query, use the value() method. Each field in the data
       returned by a SELECT statement is accessed by passing the field's position in the
       statement, starting from 0. Information about the fields can be obtained via
       QSqlDatabase::record(). For the sake of efficiency there are no functions to access a
       field by name. (The QSqlCursor class provides a higher-level interface with field access
       by name and automatic SQL generation.)

       QSqlQuery supports prepared query execution and the binding of parameter values to
       placeholders. Some databases don't support these features, so for them Qt emulates the
       required functionality. For example, the Oracle and ODBC drivers have proper prepared
       query support, and Qt makes use of it; but for databases that don't have this support, Qt
       implements the feature itself, e.g. by replacing placeholders with actual values when a
       query is executed. The exception is positional binding using named placeholders, which
       requires that the database supports prepared queries.

       Oracle databases identify placeholders by using a colon-name syntax, e.g :name. ODBC
       simply uses ? characters. Qt supports both syntaxes (although you can't mix them in the
       same query).

       Below we present the same example using each of the four different binding approaches.

       Named binding using named placeholders

	   QSqlQuery query;
	   query.prepare( "INSERT INTO atable (id, forename, surname) "
			  "VALUES (:id, :forename, :surname)" );
	   query.bindValue( ":id", 1001 );
	   query.bindValue( ":forename", "Bart" );
	   query.bindValue( ":surname", "Simpson" );
	   query.exec();

       Positional binding using named placeholders

	   QSqlQuery query;
	   query.prepare( "INSERT INTO atable (id, forename, surname) "
			  "VALUES (:id, :forename, :surname)" );
	   query.bindValue( 0, 1001 );
	   query.bindValue( 1, "Bart" );
	   query.bindValue( 2, "Simpson" );
	   query.exec();
       Note: Using positional binding with named placeholders will only work if the database
       supports prepared queries. This can be checked with QSqlDriver::hasFeature() using
       QSqlDriver::PreparedQueries as argument for driver feature.

       Binding values using positional placeholders #1

	   QSqlQuery query;
	   query.prepare( "INSERT INTO atable (id, forename, surname) "
			  "VALUES (?, ?, ?)" );
	   query.bindValue( 0, 1001 );
	   query.bindValue( 1, "Bart" );
	   query.bindValue( 2, "Simpson" );
	   query.exec();

       Binding values using positional placeholders #2

	   query.prepare( "INSERT INTO atable (id, forename, surname) "
			  "VALUES (?, ?, ?)" );
	   query.addBindValue( 1001 );
	   query.addBindValue( "Bart" );
	   query.addBindValue( "Simpson" );
	   query.exec();

       Binding values to a stored procedure This code calls a stored procedure called
       AsciiToInt(), passing it a character through its in parameter, and taking its result in
       the out parameter.

	   QSqlQuery query;
	   query.prepare( "call AsciiToInt(?, ?)" );
	   query.bindValue( 0, "A" );
	   query.bindValue( 1, 0, QSql::Out );
	   query.exec();
	   int i = query.boundValue( 1 ).toInt(); // i is 65.

       See also QSqlDatabase, QSqlCursor, QVariant, and Database Classes.

MEMBER FUNCTION DOCUMENTATION
QSqlQuery::QSqlQuery ( QSqlResult * r )
       Creates a QSqlQuery object which uses the QSqlResult r to communicate with a database.

QSqlQuery::QSqlQuery ( const QString & query = QString::null, QSqlDatabase * db = 0 )
       Creates a QSqlQuery object using the SQL query and the database db. If db is 0, (the
       default), the application's default database is used. If query is not a null string, it
       will be executed.

       See also QSqlDatabase.

explicit QSqlQuery::QSqlQuery ( QSqlDatabase * db )
       Creates a QSqlQuery object using the database db. If db is 0, the application's default
       database is used.

       See also QSqlDatabase.

QSqlQuery::QSqlQuery ( const QSqlQuery & other )
       Constructs a copy of other.

QSqlQuery::~QSqlQuery () [virtual]
       Destroys the object and frees any allocated resources.

void QSqlQuery::addBindValue ( const QVariant & val, QSql::ParameterType type )
       Adds the value val to the list of values when using positional value binding. The order of
       the addBindValue() calls determines which placeholder a value will be bound to in the
       prepared query. If type is QSql::Out or QSql::InOut, the placeholder will be overwritten
       with data from the database after the exec() call.

       See also bindValue(), prepare(), and exec().

void QSqlQuery::addBindValue ( const QVariant & val )
       This is an overloaded member function, provided for convenience. It behaves essentially
       like the above function.

       Binds the placeholder with type QSql::In.

void QSqlQuery::afterSeek () [virtual protected]
       Protected virtual function called after the internal record pointer is moved to a new
       record. The default implementation does nothing.

int QSqlQuery::at () const
       Returns the current internal position of the query. The first record is at position zero.
       If the position is invalid, a QSql::Location will be returned indicating the invalid
       position.

       See also prev(), next(), first(), last(), seek(), isActive(), and isValid().

       Example: sql/overview/navigating/main.cpp.

void QSqlQuery::beforeSeek () [virtual protected]
       Protected virtual function called before the internal record pointer is moved to a new
       record. The default implementation does nothing.

void QSqlQuery::bindValue ( const QString & placeholder, const QVariant & val,
       QSql::ParameterType type )
       Set the placeholder placeholder to be bound to value val in the prepared statement. Note
       that the placeholder mark (e.g :) must be included when specifying the placeholder name.
       If type is QSql::Out or QSql::InOut, the placeholder will be overwritten with data from
       the database after the exec() call.

       See also addBindValue(), prepare(), and exec().

void QSqlQuery::bindValue ( const QString & placeholder, const QVariant & val )
       This is an overloaded member function, provided for convenience. It behaves essentially
       like the above function.

       Binds the placeholder with type QSql::In.

void QSqlQuery::bindValue ( int pos, const QVariant & val )
       This is an overloaded member function, provided for convenience. It behaves essentially
       like the above function.

       Binds the placeholder at position pos with type QSql::In.

void QSqlQuery::bindValue ( int pos, const QVariant & val, QSql::ParameterType type )
       This is an overloaded member function, provided for convenience. It behaves essentially
       like the above function.

       Set the placeholder in position pos to be bound to value val in the prepared statement.
       Field numbering starts at 0. If type is QSql::Out or QSql::InOut, the placeholder will be
       overwritten with data from the database after the exec() call.

       See also addBindValue(), prepare(), and exec().

QVariant QSqlQuery::boundValue ( const QString & placeholder ) const
       Returns the value for the placeholder.

QVariant QSqlQuery::boundValue ( int pos ) const
       This is an overloaded member function, provided for convenience. It behaves essentially
       like the above function.

       Returns the value for the placeholder at position pos.

QMap<;QString, QVariant> QSqlQuery::boundValues () const
       Returns a map of the bound values.

       The bound values can be examined in the following way:

	   QSqlQuery query;
	   ...
	   // Examine the bound values - bound using named binding
	   QMap<QString, QVariant>::ConstIterator it;
	   QMap<QString, QVariant> vals = query.boundValues();
	   for ( it = vals.begin(); it != vals.end(); ++it )
	       qWarning( "Placeholder: " + it.key() + ", Value: " + (*it).toString() );
	   ...
	   // Examine the bound values - bound using positional binding
	   QValueList<QVariant>::ConstIterator it;
	   QValueList<QVariant> list = query.boundValues().values();
	   int i = 0;
	   for ( it = list.begin(); it != list.end(); ++it )
	       qWarning( "Placeholder pos: %d, Value: " + (*it).toString(), i++ );
	   ...

const QSqlDriver * QSqlQuery::driver () const
       Returns the database driver associated with the query.

bool QSqlQuery::exec ( const QString & query ) [virtual]
       Executes the SQL in query. Returns TRUE and sets the query state to active if the query
       was successful; otherwise returns FALSE and sets the query state to inactive. The query
       string must use syntax appropriate for the SQL database being queried, for example,
       standard SQL.

       After the query is executed, the query is positioned on an invalid record, and must be
       navigated to a valid record before data values can be retrieved, e.g. using next().

       Note that the last error for this query is reset when exec() is called.

       See also isActive(), isValid(), next(), prev(), first(), last(), and seek().

       Examples:

bool QSqlQuery::exec ()
       This is an overloaded member function, provided for convenience. It behaves essentially
       like the above function.

       Executes a previously prepared SQL query. Returns TRUE if the query executed successfully;
       otherwise returns FALSE.

       See also prepare(), bindValue(), and addBindValue().

QString QSqlQuery::executedQuery () const
       Returns the last query that was executed.

       In most cases this function returns the same as lastQuery(). If a prepared query with
       placeholders is executed on a DBMS that does not support it, the preparation of this query
       is emulated. The placeholders in the original query are replaced with their bound values
       to form a new query. This function returns the modified query. Useful for debugging
       purposes.

       See also lastQuery().

bool QSqlQuery::first () [virtual]
       Retrieves the first record in the result, if available, and positions the query on the
       retrieved record. Note that the result must be in an active state and isSelect() must
       return TRUE before calling this function or it will do nothing and return FALSE. Returns
       TRUE if successful. If unsuccessful the query position is set to an invalid position and
       FALSE is returned.

       See also next(), prev(), last(), seek(), at(), isActive(), and isValid().

       Example: sql/overview/navigating/main.cpp.

bool QSqlQuery::isActive () const
       Returns TRUE if the query is currently active; otherwise returns FALSE.

       Examples:

bool QSqlQuery::isForwardOnly () const
       Returns TRUE if you can only scroll forward through a result set; otherwise returns FALSE.

       See also setForwardOnly().

bool QSqlQuery::isNull ( int field ) const
       Returns TRUE if the query is active and positioned on a valid record and the field is
       NULL; otherwise returns FALSE. Note that for some drivers isNull() will not return
       accurate information until after an attempt is made to retrieve data.

       See also isActive(), isValid(), and value().

bool QSqlQuery::isSelect () const
       Returns TRUE if the current query is a SELECT statement; otherwise returns FALSE.

bool QSqlQuery::isValid () const
       Returns TRUE if the query is currently positioned on a valid record; otherwise returns
       FALSE.

bool QSqlQuery::last () [virtual]
       Retrieves the last record in the result, if available, and positions the query on the
       retrieved record. Note that the result must be in an active state and isSelect() must
       return TRUE before calling this function or it will do nothing and return FALSE. Returns
       TRUE if successful. If unsuccessful the query position is set to an invalid position and
       FALSE is returned.

       See also next(), prev(), first(), seek(), at(), isActive(), and isValid().

       Example: sql/overview/navigating/main.cpp.

QSqlError QSqlQuery::lastError () const
       Returns error information about the last error (if any) that occurred.

       See also QSqlError.

QString QSqlQuery::lastQuery () const
       Returns the text of the current query being used, or QString::null if there is no current
       query text.

       See also executedQuery().

bool QSqlQuery::next () [virtual]
       Retrieves the next record in the result, if available, and positions the query on the
       retrieved record. Note that the result must be in an active state and isSelect() must
       return TRUE before calling this function or it will do nothing and return FALSE.

       The following rules apply:

       If the result is currently located before the first record, e.g. immediately after a query
       is executed, an attempt is made to retrieve the first record.

       If the result is currently located after the last record, there is no change and FALSE is
       returned.

       If the result is located somewhere in the middle, an attempt is made to retrieve the next
       record.

       If the record could not be retrieved, the result is positioned after the last record and
       FALSE is returned. If the record is successfully retrieved, TRUE is returned.

       See also prev(), first(), last(), seek(), at(), isActive(), and isValid().

       Examples:

int QSqlQuery::numRowsAffected () const
       Returns the number of rows affected by the result's SQL statement, or -1 if it cannot be
       determined. Note that for SELECT statements, the value is undefined; see size() instead.
       If the query is not active (isActive() returns FALSE), -1 is returned.

       See also size() and QSqlDriver::hasFeature().

       Examples:

QSqlQuery &; QSqlQuery::operator= ( const QSqlQuery & other )
       Assigns other to the query.

bool QSqlQuery::prepare ( const QString & query )
       Prepares the SQL query query for execution. The query may contain placeholders for binding
       values. Both Oracle style colon-name (e.g. :surname), and ODBC style (e.g. ?) placeholders
       are supported; but they cannot be mixed in the same query. See the Description for
       examples.

       See also exec(), bindValue(), and addBindValue().

bool QSqlQuery::prev () [virtual]
       Retrieves the previous record in the result, if available, and positions the query on the
       retrieved record. Note that the result must be in an active state and isSelect() must
       return TRUE before calling this function or it will do nothing and return FALSE.

       The following rules apply:

       If the result is currently located before the first record, there is no change and FALSE
       is returned.

       If the result is currently located after the last record, an attempt is made to retrieve
       the last record.

       If the result is somewhere in the middle, an attempt is made to retrieve the previous
       record.

       If the record could not be retrieved, the result is positioned before the first record and
       FALSE is returned. If the record is successfully retrieved, TRUE is returned.

       See also next(), first(), last(), seek(), at(), isActive(), and isValid().

const QSqlResult * QSqlQuery::result () const
       Returns the result associated with the query.

bool QSqlQuery::seek ( int i, bool relative = FALSE ) [virtual]
       Retrieves the record at position (offset) i, if available, and positions the query on the
       retrieved record. The first record is at position 0. Note that the query must be in an
       active state and isSelect() must return TRUE before calling this function.

       If relative is FALSE (the default), the following rules apply:

       If i is negative, the result is positioned before the first record and FALSE is returned.

       Otherwise, an attempt is made to move to the record at position i. If the record at
       position i could not be retrieved, the result is positioned after the last record and
       FALSE is returned. If the record is successfully retrieved, TRUE is returned.

       If relative is TRUE, the following rules apply:

       If the result is currently positioned before the first record or on the first record, and
       i is negative, there is no change, and FALSE is returned.

       If the result is currently located after the last record, and i is positive, there is no
       change, and FALSE is returned.

       If the result is currently located somewhere in the middle, and the relative offset i
       moves the result below zero, the result is positioned before the first record and FALSE is
       returned.

       Otherwise, an attempt is made to move to the record i records ahead of the current record
       (or i records behind the current record if i is negative). If the record at offset i could
       not be retrieved, the result is positioned after the last record if i >= 0, (or before the
       first record if i is negative), and FALSE is returned. If the record is successfully
       retrieved, TRUE is returned.

       See also next(), prev(), first(), last(), at(), isActive(), and isValid().

       Example: sql/overview/navigating/main.cpp.

void QSqlQuery::setForwardOnly ( bool forward )
       Sets forward only mode to forward. If forward is TRUE only next(), and seek() with
       positive values, are allowed for navigating the results. Forward only mode needs far less
       memory since results do not need to be cached.

       Forward only mode is off by default.

       Forward only mode cannot be used with data aware widgets like QDataTable, since they must
       to be able to scroll backward as well as forward.

       See also isForwardOnly(), next(), and seek().

int QSqlQuery::size () const
       Returns the size of the result, (number of rows returned), or -1 if the size cannot be
       determined or if the database does not support reporting information about query sizes.
       Note that for non-SELECT statements (isSelect() returns FALSE), size() will return -1. If
       the query is not active (isActive() returns FALSE), -1 is returned.

       To determine the number of rows affected by a non-SELECT statement, use numRowsAffected().

       See also isActive(), numRowsAffected(), and QSqlDriver::hasFeature().

       Example: sql/overview/navigating/main.cpp.

QVariant QSqlQuery::value ( int i ) const [virtual]
       Returns the value of the i-th field in the query (zero based).

       The fields are numbered from left to right using the text of the SELECT statement, e.g. in
       SELECT forename, surname FROM people, field 0 is forename and field 1 is surname. Using
       SELECT * is not recommended because the order of the fields in the query is undefined.

       An invalid QVariant is returned if field i does not exist, if the query is inactive, or if
       the query is positioned on an invalid record.

       See also prev(), next(), first(), last(), seek(), isActive(), and isValid().

       Examples:

SEE ALSO
       http://doc.trolltech.com/qsqlquery.html http://www.trolltech.com/faq/tech.html

COPYRIGHT
       Copyright 1992-2007 Trolltech ASA, http://www.trolltech.com.  See the license file
       included in the distribution for a complete license statement.

AUTHOR
       Generated automatically from the source code.

BUGS
       If you find a bug in Qt, please report it as described in
       http://doc.trolltech.com/bughowto.html.	Good bug reports help us to help you. Thank you.

       The definitive Qt documentation is provided in HTML format; it is located at
       $QTDIR/doc/html and can be read using Qt Assistant or with a web browser. This man page is
       provided as a convenience for those users who prefer man pages, although this format is
       not officially supported by Trolltech.

       If you find errors in this manual page, please report them to qt-bugs@trolltech.com.
       Please include the name of the manual page (qsqlquery.3qt) and the Qt version (3.3.8).

Trolltech AS				 2 February 2007			   QSqlQuery(3qt)
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