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< td align = "right" valign = "center" > < img src = "logo32.png" align = "right" width = "64" height = "32" border = "0" > < / td > < / tr > < / table > < h1 align = center > TQSqlQuery Class Reference< br > < small > [< a href = "sql.html" > sql module< / a > ]< / small > < / h1 >
< p > The TQSqlQuery class provides a means of executing and
manipulating SQL statements.
< a href = "#details" > More...< / a >
< p > < tt > #include < < a href = "qsqlquery-h.html" > ntqsqlquery.h< / a > > < / tt >
< p > Inherited by < a href = "ntqsqlcursor.html" > TQSqlCursor< / a > .
< p > < a href = "qsqlquery-members.html" > List of all member functions.< / a >
< h2 > Public Members< / h2 >
< ul >
< li class = fn > < a href = "#TQSqlQuery" > < b > TQSqlQuery< / b > < / a > ( TQSqlResult * r )< / li >
< li class = fn > < a href = "#TQSqlQuery-2" > < b > TQSqlQuery< / b > < / a > ( const TQString & query = TQString::null, TQSqlDatabase * db = 0 )< / li >
< li class = fn > explicit < a href = "#TQSqlQuery-3" > < b > TQSqlQuery< / b > < / a > ( TQSqlDatabase * db )< / li >
< li class = fn > < a href = "#TQSqlQuery-4" > < b > TQSqlQuery< / b > < / a > ( const TQSqlQuery & other )< / li >
< li class = fn > TQSqlQuery & < a href = "#operator-eq" > < b > operator=< / b > < / a > ( const TQSqlQuery & other )< / li >
< li class = fn > virtual < a href = "#~TQSqlQuery" > < b > ~TQSqlQuery< / b > < / a > ()< / li >
< li class = fn > bool < a href = "#isValid" > < b > isValid< / b > < / a > () const< / li >
< li class = fn > bool < a href = "#isActive" > < b > isActive< / b > < / a > () const< / li >
< li class = fn > bool < a href = "#isNull" > < b > isNull< / b > < / a > ( int field ) const< / li >
< li class = fn > int < a href = "#at" > < b > at< / b > < / a > () const< / li >
< li class = fn > TQString < a href = "#lastQuery" > < b > lastQuery< / b > < / a > () const< / li >
< li class = fn > int < a href = "#numRowsAffected" > < b > numRowsAffected< / b > < / a > () const< / li >
< li class = fn > TQSqlError < a href = "#lastError" > < b > lastError< / b > < / a > () const< / li >
< li class = fn > bool < a href = "#isSelect" > < b > isSelect< / b > < / a > () const< / li >
< li class = fn > int < a href = "#size" > < b > size< / b > < / a > () const< / li >
< li class = fn > const TQSqlDriver * < a href = "#driver" > < b > driver< / b > < / a > () const< / li >
< li class = fn > const TQSqlResult * < a href = "#result" > < b > result< / b > < / a > () const< / li >
< li class = fn > bool < a href = "#isForwardOnly" > < b > isForwardOnly< / b > < / a > () const< / li >
< li class = fn > void < a href = "#setForwardOnly" > < b > setForwardOnly< / b > < / a > ( bool forward )< / li >
< li class = fn > virtual bool < a href = "#exec" > < b > exec< / b > < / a > ( const TQString & query )< / li >
< li class = fn > virtual TQVariant < a href = "#value" > < b > value< / b > < / a > ( int i ) const< / li >
< li class = fn > virtual bool < a href = "#seek" > < b > seek< / b > < / a > ( int i, bool relative = FALSE )< / li >
< li class = fn > virtual bool < a href = "#next" > < b > next< / b > < / a > ()< / li >
< li class = fn > virtual bool < a href = "#prev" > < b > prev< / b > < / a > ()< / li >
< li class = fn > virtual bool < a href = "#first" > < b > first< / b > < / a > ()< / li >
< li class = fn > virtual bool < a href = "#last" > < b > last< / b > < / a > ()< / li >
< li class = fn > bool < a href = "#exec-2" > < b > exec< / b > < / a > ()< / li >
< li class = fn > bool < a href = "#prepare" > < b > prepare< / b > < / a > ( const TQString & query )< / li >
< li class = fn > void < a href = "#bindValue-2" > < b > bindValue< / b > < / a > ( const TQString & placeholder, const TQVariant & val )< / li >
< li class = fn > void < a href = "#bindValue-3" > < b > bindValue< / b > < / a > ( int pos, const TQVariant & val )< / li >
< li class = fn > void < a href = "#addBindValue-2" > < b > addBindValue< / b > < / a > ( const TQVariant & val )< / li >
< li class = fn > void < a href = "#bindValue" > < b > bindValue< / b > < / a > ( const TQString & placeholder, const TQVariant & val, TQSql::ParameterType type )< / li >
< li class = fn > void < a href = "#bindValue-4" > < b > bindValue< / b > < / a > ( int pos, const TQVariant & val, TQSql::ParameterType type )< / li >
< li class = fn > void < a href = "#addBindValue" > < b > addBindValue< / b > < / a > ( const TQVariant & val, TQSql::ParameterType type )< / li >
< li class = fn > TQVariant < a href = "#boundValue" > < b > boundValue< / b > < / a > ( const TQString & placeholder ) const< / li >
< li class = fn > TQVariant < a href = "#boundValue-2" > < b > boundValue< / b > < / a > ( int pos ) const< / li >
< li class = fn > TQMap< TQString, TQVariant> < a href = "#boundValues" > < b > boundValues< / b > < / a > () const< / li >
< li class = fn > TQString < a href = "#executedQuery" > < b > executedQuery< / b > < / a > () const< / li >
< / ul >
< h2 > Protected Members< / h2 >
< ul >
< li class = fn > virtual void < a href = "#beforeSeek" > < b > beforeSeek< / b > < / a > ()< / li >
< li class = fn > virtual void < a href = "#afterSeek" > < b > afterSeek< / b > < / a > ()< / li >
< / ul >
< hr > < a name = "details" > < / a > < h2 > Detailed Description< / h2 >
The TQSqlQuery class provides a means of executing and
manipulating SQL statements.
< p >
< p > TQSqlQuery encapsulates the functionality involved in creating,
navigating and retrieving data from SQL queries which are executed
on a < a href = "ntqsqldatabase.html" > TQSqlDatabase< / a > . It can be used to execute DML (data
manipulation language) statements, e.g. < tt > SELECT< / tt > , < tt > INSERT< / tt > , < tt > UPDATE< / tt > and < tt > DELETE< / tt > , and also DDL (data definition language)
statements, e.g. < tt > CREATE TABLE< / tt > . It can also be used to
execute database-specific commands which are not standard SQL
(e.g. < tt > SET DATESTYLE=ISO< / tt > for PostgreSQL).
< p > Successfully executed SQL statements set the query's state to
active (< a href = "#isActive" > isActive< / a > () 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 < a href = "#isValid" > isValid< / a > ()
returns TRUE) before values can be retrieved.
< p > Navigating records is performed with the following functions:
< p > < ul >
< li > < a href = "#next" > next< / a > ()
< li > < a href = "#prev" > prev< / a > ()
< li > < a href = "#first" > first< / a > ()
< li > < a href = "#last" > last< / a > ()
< li > < tt > < / tt > < a href = "#seek" > seek< / a > (int)
< / ul >
< p > 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 < a href = "#next" > next< / a > () or
using < a href = "#seek" > seek< / a > () with a positive offset, you can use < a href = "#setForwardOnly" > setForwardOnly< / a > ()
and save a significant amount of memory overhead. Once an active
query is positioned on a valid record, data can be retrieved using
< a href = "#value" > value< / a > (). All data is transferred from the SQL backend using
TQVariants.
< p > For example:
< p > < pre >
TQSqlQuery query( "SELECT name FROM customer" );
while ( query.< a href = "#next" > next< / a > () ) {
< a href = "ntqstring.html" > TQString< / a > name = query.< a href = "#value" > value< / a > (0).toString();
doSomething( name );
}
< / pre >
< p > 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 < a href = "ntqsqldatabase.html#record" > TQSqlDatabase::record< / a > ().
For the sake of efficiency there are no functions to access a field
by name. (The < a href = "ntqsqlcursor.html" > TQSqlCursor< / a > class provides a higher-level interface
with field access by name and automatic SQL generation.)
< p > TQSqlQuery supports prepared query execution and the binding of
parameter values to placeholders. Some databases don't support
these features, so for them TQt emulates the required
functionality. For example, the Oracle and ODBC drivers have
proper prepared query support, and TQt makes use of it; but for
databases that don't have this support, TQt 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.
< p > Oracle databases identify placeholders by using a colon-name
syntax, e.g < tt > :name< / tt > . ODBC simply uses < tt > ?< / tt > characters. TQt
supports both syntaxes (although you can't mix them in the same
query).
< p > Below we present the same example using each of the four different
binding approaches.
< p > < b > Named binding using named placeholders< / b >
< pre >
TQSqlQuery query;
query.< a href = "#prepare" > prepare< / a > ( "INSERT INTO atable (id, forename, surname) "
"VALUES (:id, :forename, :surname)" );
query.< a href = "#bindValue" > bindValue< / a > ( ":id", 1001 );
query.< a href = "#bindValue" > bindValue< / a > ( ":forename", "Bart" );
query.< a href = "#bindValue" > bindValue< / a > ( ":surname", "Simpson" );
query.< a href = "#exec" > exec< / a > ();
< / pre >
< p > < b > Positional binding using named placeholders< / b >
< pre >
TQSqlQuery query;
query.< a href = "#prepare" > prepare< / a > ( "INSERT INTO atable (id, forename, surname) "
"VALUES (:id, :forename, :surname)" );
query.< a href = "#bindValue" > bindValue< / a > ( 0, 1001 );
query.< a href = "#bindValue" > bindValue< / a > ( 1, "Bart" );
query.< a href = "#bindValue" > bindValue< / a > ( 2, "Simpson" );
query.< a href = "#exec" > exec< / a > ();
< / pre >
< b > Note:< / b > Using positional binding with named placeholders will
only work if the database supports prepared queries. This can be
checked with < a href = "ntqsqldriver.html#hasFeature" > TQSqlDriver::hasFeature< / a > () using TQSqlDriver::PreparedQueries
as argument for driver feature.
< p > < b > Binding values using positional placeholders #1< / b >
< pre >
TQSqlQuery query;
query.< a href = "#prepare" > prepare< / a > ( "INSERT INTO atable (id, forename, surname) "
"VALUES (?, ?, ?)" );
query.< a href = "#bindValue" > bindValue< / a > ( 0, 1001 );
query.< a href = "#bindValue" > bindValue< / a > ( 1, "Bart" );
query.< a href = "#bindValue" > bindValue< / a > ( 2, "Simpson" );
query.< a href = "#exec" > exec< / a > ();
< / pre >
< p > < b > Binding values using positional placeholders #2< / b >
< pre >
query.prepare( "INSERT INTO atable (id, forename, surname) "
"VALUES (?, ?, ?)" );
query.addBindValue( 1001 );
query.addBindValue( "Bart" );
query.addBindValue( "Simpson" );
query.exec();
< / pre >
< p > < b > Binding values to a stored procedure< / b >
This code calls a stored procedure called < tt > AsciiToInt()< / tt > , passing
it a character through its in parameter, and taking its result in
the out parameter.
< pre >
TQSqlQuery query;
query.< a href = "#prepare" > prepare< / a > ( "call AsciiToInt(?, ?)" );
query.< a href = "#bindValue" > bindValue< / a > ( 0, "A" );
query.< a href = "#bindValue" > bindValue< / a > ( 1, 0, TQSql::Out );
query.< a href = "#exec" > exec< / a > ();
int i = query.< a href = "#boundValue" > boundValue< / a > ( 1 ).toInt(); // i is 65.
< / pre >
< p > < p > See also < a href = "ntqsqldatabase.html" > TQSqlDatabase< / a > , < a href = "ntqsqlcursor.html" > TQSqlCursor< / a > , < a href = "ntqvariant.html" > TQVariant< / a > , and < a href = "database.html" > Database Classes< / a > .
< hr > < h2 > Member Function Documentation< / h2 >
< h3 class = fn > < a name = "TQSqlQuery" > < / a > TQSqlQuery::TQSqlQuery ( < a href = "ntqsqlresult.html" > TQSqlResult< / a > * r )
< / h3 >
Creates a TQSqlQuery object which uses the < a href = "ntqsqlresult.html" > TQSqlResult< / a > < em > r< / em > to
communicate with a database.
< h3 class = fn > < a name = "TQSqlQuery-2" > < / a > TQSqlQuery::TQSqlQuery ( const < a href = "ntqstring.html" > TQString< / a > & query = TQString::null, < a href = "ntqsqldatabase.html" > TQSqlDatabase< / a > * db = 0 )
< / h3 >
Creates a TQSqlQuery object using the SQL < em > query< / em > and the database
< em > db< / em > . If < em > db< / em > is 0, (the default), the application's default
database is used. If < em > query< / em > is not a null string, it will be
executed.
< p > < p > See also < a href = "ntqsqldatabase.html" > TQSqlDatabase< / a > .
< h3 class = fn > explicit < a name = "TQSqlQuery-3" > < / a > TQSqlQuery::TQSqlQuery ( < a href = "ntqsqldatabase.html" > TQSqlDatabase< / a > * db )
< / h3 >
Creates a TQSqlQuery object using the database < em > db< / em > . If < em > db< / em > is
0, the application's default database is used.
< p > < p > See also < a href = "ntqsqldatabase.html" > TQSqlDatabase< / a > .
< h3 class = fn > < a name = "TQSqlQuery-4" > < / a > TQSqlQuery::TQSqlQuery ( const < a href = "ntqsqlquery.html" > TQSqlQuery< / a > & other )
< / h3 >
Constructs a copy of < em > other< / em > .
< h3 class = fn > < a name = "~TQSqlQuery" > < / a > TQSqlQuery::~TQSqlQuery ()< tt > [virtual]< / tt >
< / h3 >
Destroys the object and frees any allocated resources.
< h3 class = fn > void < a name = "addBindValue" > < / a > TQSqlQuery::addBindValue ( const < a href = "ntqvariant.html" > TQVariant< / a > & val, < a href = "ntqsql.html#ParameterType-enum" > TQSql::ParameterType< / a > type )
< / h3 >
Adds the value < em > val< / em > to the list of values when using positional
value binding. The order of the < a href = "#addBindValue" > addBindValue< / a > () calls determines
which placeholder a value will be bound to in the prepared query.
If < em > type< / em > is < a href = "ntqsql.html#ParameterType-enum" > TQSql::Out< / a > or < a href = "ntqsql.html#ParameterType-enum" > TQSql::InOut< / a > , the placeholder will
be overwritten with data from the database after the < a href = "#exec" > exec< / a > () call.
< p > < p > See also < a href = "#bindValue" > bindValue< / a > (), < a href = "#prepare" > prepare< / a > (), and < a href = "#exec" > exec< / a > ().
< h3 class = fn > void < a name = "addBindValue-2" > < / a > TQSqlQuery::addBindValue ( const < a href = "ntqvariant.html" > TQVariant< / a > & val )
< / h3 >
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
< p > Binds the placeholder with type < a href = "ntqsql.html#ParameterType-enum" > TQSql::In< / a > .
< h3 class = fn > void < a name = "afterSeek" > < / a > TQSqlQuery::afterSeek ()< tt > [virtual protected]< / tt >
< / h3 >
Protected virtual function called after the internal record
pointer is moved to a new record. The default implementation does
nothing.
< h3 class = fn > int < a name = "at" > < / a > TQSqlQuery::at () const
< / h3 >
Returns the current internal position of the query. The first
record is at position zero. If the position is invalid, a
TQSql::Location will be returned indicating the invalid position.
< p > < p > See also < a href = "#prev" > prev< / a > (), < a href = "#next" > next< / a > (), < a href = "#first" > first< / a > (), < a href = "#last" > last< / a > (), < a href = "#seek" > seek< / a > (), < a href = "#isActive" > isActive< / a > (), and < a href = "#isValid" > isValid< / a > ().
< p > Example: < a href = "sql.html#x2169" > sql/overview/navigating/main.cpp< / a > .
< h3 class = fn > void < a name = "beforeSeek" > < / a > TQSqlQuery::beforeSeek ()< tt > [virtual protected]< / tt >
< / h3 >
Protected virtual function called before the internal record
pointer is moved to a new record. The default implementation does
nothing.
< h3 class = fn > void < a name = "bindValue" > < / a > TQSqlQuery::bindValue ( const < a href = "ntqstring.html" > TQString< / a > & placeholder, const < a href = "ntqvariant.html" > TQVariant< / a > & val, < a href = "ntqsql.html#ParameterType-enum" > TQSql::ParameterType< / a > type )
< / h3 >
Set the placeholder < em > placeholder< / em > to be bound to value < em > val< / em > in
the prepared statement. Note that the placeholder mark (e.g < tt > :< / tt > )
must be included when specifying the placeholder name. If < em > type< / em >
is < a href = "ntqsql.html#ParameterType-enum" > TQSql::Out< / a > or < a href = "ntqsql.html#ParameterType-enum" > TQSql::InOut< / a > , the placeholder will be
overwritten with data from the database after the < a href = "#exec" > exec< / a > () call.
< p > < p > See also < a href = "#addBindValue" > addBindValue< / a > (), < a href = "#prepare" > prepare< / a > (), and < a href = "#exec" > exec< / a > ().
< h3 class = fn > void < a name = "bindValue-2" > < / a > TQSqlQuery::bindValue ( const < a href = "ntqstring.html" > TQString< / a > & placeholder, const < a href = "ntqvariant.html" > TQVariant< / a > & val )
< / h3 >
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
< p > Binds the placeholder with type < a href = "ntqsql.html#ParameterType-enum" > TQSql::In< / a > .
< h3 class = fn > void < a name = "bindValue-3" > < / a > TQSqlQuery::bindValue ( int pos, const < a href = "ntqvariant.html" > TQVariant< / a > & val )
< / h3 >
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
< p > Binds the placeholder at position < em > pos< / em > with type < a href = "ntqsql.html#ParameterType-enum" > TQSql::In< / a > .
< h3 class = fn > void < a name = "bindValue-4" > < / a > TQSqlQuery::bindValue ( int pos, const < a href = "ntqvariant.html" > TQVariant< / a > & val, < a href = "ntqsql.html#ParameterType-enum" > TQSql::ParameterType< / a > type )
< / h3 >
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
< p > Set the placeholder in position < em > pos< / em > to be bound to value < em > val< / em >
in the prepared statement. Field numbering starts at 0. If < em > type< / em >
is < a href = "ntqsql.html#ParameterType-enum" > TQSql::Out< / a > or < a href = "ntqsql.html#ParameterType-enum" > TQSql::InOut< / a > , the placeholder will be
overwritten with data from the database after the < a href = "#exec" > exec< / a > () call.
< p > < p > See also < a href = "#addBindValue" > addBindValue< / a > (), < a href = "#prepare" > prepare< / a > (), and < a href = "#exec" > exec< / a > ().
< h3 class = fn > < a href = "ntqvariant.html" > TQVariant< / a > < a name = "boundValue" > < / a > TQSqlQuery::boundValue ( const < a href = "ntqstring.html" > TQString< / a > & placeholder ) const
< / h3 >
Returns the value for the < em > placeholder< / em > .
< h3 class = fn > < a href = "ntqvariant.html" > TQVariant< / a > < a name = "boundValue-2" > < / a > TQSqlQuery::boundValue ( int pos ) const
< / h3 >
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
< p > Returns the value for the placeholder at position < em > pos< / em > .
< h3 class = fn > < a href = "ntqmap.html" > TQMap< / a > < TQString, TQVariant> < a name = "boundValues" > < / a > TQSqlQuery::boundValues () const
< / h3 >
Returns a map of the bound values.
< p > The bound values can be examined in the following way:
< pre >
TQSqlQuery query;
...
// Examine the bound values - bound using named binding
TQMap< TQString, TQVariant> ::ConstIterator it;
< a href = "ntqmap.html" > TQMap< / a > < TQString, TQVariant> vals = query.< a href = "#boundValues" > boundValues< / a > ();
for ( it = vals.< a href = "ntqmap.html#begin" > begin< / a > (); it != vals.< a href = "ntqmap.html#end" > end< / a > (); ++it )
< a href = "ntqapplication.html#qWarning" > tqWarning< / a > ( "Placeholder: " + it.key() + ", Value: " + (*it).toString() );
...
// Examine the bound values - bound using positional binding
TQValueList< TQVariant> ::ConstIterator it;
< a href = "ntqvaluelist.html" > TQValueList< / a > < TQVariant> list = query.< a href = "#boundValues" > boundValues< / a > ().values();
int i = 0;
for ( it = list.< a href = "ntqvaluelist.html#begin" > begin< / a > (); it != list.< a href = "ntqvaluelist.html#end" > end< / a > (); ++it )
< a href = "ntqapplication.html#qWarning" > tqWarning< / a > ( "Placeholder pos: %d, Value: " + (*it).toString(), i++ );
...
< / pre >
< h3 class = fn > const < a href = "ntqsqldriver.html" > TQSqlDriver< / a > * < a name = "driver" > < / a > TQSqlQuery::driver () const
< / h3 >
Returns the database driver associated with the query.
< h3 class = fn > bool < a name = "exec" > < / a > TQSqlQuery::exec ( const < a href = "ntqstring.html" > TQString< / a > & query )< tt > [virtual]< / tt >
< / h3 >
Executes the SQL in < em > query< / em > . 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 < em > query< / em > string
must use syntax appropriate for the SQL database being queried,
for example, standard SQL.
< p > After the query is executed, the query is positioned on an < em > invalid< / em > record, and must be navigated to a valid record before
data values can be retrieved, e.g. using < a href = "#next" > next< / a > ().
< p > Note that the last error for this query is reset when < a href = "#exec" > exec< / a > () is
called.
< p > < p > See also < a href = "#isActive" > isActive< / a > (), < a href = "#isValid" > isValid< / a > (), < a href = "#next" > next< / a > (), < a href = "#prev" > prev< / a > (), < a href = "#first" > first< / a > (), < a href = "#last" > last< / a > (), and < a href = "#seek" > seek< / a > ().
< p > Examples: < a href = "sql.html#x2157" > sql/overview/basicbrowsing/main.cpp< / a > , < a href = "sql.html#x2161" > sql/overview/basicbrowsing2/main.cpp< / a > , < a href = "sql.html#x2166" > sql/overview/basicdatamanip/main.cpp< / a > , and < a href = "sql.html#x2154" > sql/overview/connection.cpp< / a > .
< h3 class = fn > bool < a name = "exec-2" > < / a > TQSqlQuery::exec ()
< / h3 >
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
< p > Executes a previously prepared SQL query. Returns TRUE if the
query executed successfully; otherwise returns FALSE.
< p > < p > See also < a href = "#prepare" > prepare< / a > (), < a href = "#bindValue" > bindValue< / a > (), and < a href = "#addBindValue" > addBindValue< / a > ().
< h3 class = fn > < a href = "ntqstring.html" > TQString< / a > < a name = "executedQuery" > < / a > TQSqlQuery::executedQuery () const
< / h3 >
Returns the last query that was executed.
< p > In most cases this function returns the same as < a href = "#lastQuery" > lastQuery< / a > (). 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.
< p > < p > See also < a href = "#lastQuery" > lastQuery< / a > ().
< h3 class = fn > bool < a name = "first" > < / a > TQSqlQuery::first ()< tt > [virtual]< / tt >
< / h3 >
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 < a href = "#isSelect" > isSelect< / a > () 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.
< p > < p > See also < a href = "#next" > next< / a > (), < a href = "#prev" > prev< / a > (), < a href = "#last" > last< / a > (), < a href = "#seek" > seek< / a > (), < a href = "#at" > at< / a > (), < a href = "#isActive" > isActive< / a > (), and < a href = "#isValid" > isValid< / a > ().
< p > Example: < a href = "sql.html#x2170" > sql/overview/navigating/main.cpp< / a > .
< h3 class = fn > bool < a name = "isActive" > < / a > TQSqlQuery::isActive () const
< / h3 >
Returns TRUE if the query is currently active; otherwise returns
FALSE.
< p > Examples: < a href = "sql.html#x2158" > sql/overview/basicbrowsing/main.cpp< / a > , < a href = "sql.html#x2162" > sql/overview/basicbrowsing2/main.cpp< / a > , < a href = "sql.html#x2167" > sql/overview/basicdatamanip/main.cpp< / a > , < a href = "sql.html#x2171" > sql/overview/navigating/main.cpp< / a > , and < a href = "sql.html#x2175" > sql/overview/retrieve1/main.cpp< / a > .
< h3 class = fn > bool < a name = "isForwardOnly" > < / a > TQSqlQuery::isForwardOnly () const
< / h3 >
Returns TRUE if you can only scroll < em > forward< / em > through a result
set; otherwise returns FALSE.
< p > < p > See also < a href = "#setForwardOnly" > setForwardOnly< / a > ().
< h3 class = fn > bool < a name = "isNull" > < / a > TQSqlQuery::isNull ( int field ) const
< / h3 >
Returns TRUE if the query is active and positioned on a valid
record and the < em > field< / em > is NULL; otherwise returns FALSE. Note
that for some drivers < a href = "#isNull" > isNull< / a > () will not return accurate
information until after an attempt is made to retrieve data.
< p > < p > See also < a href = "#isActive" > isActive< / a > (), < a href = "#isValid" > isValid< / a > (), and < a href = "#value" > value< / a > ().
< h3 class = fn > bool < a name = "isSelect" > < / a > TQSqlQuery::isSelect () const
< / h3 >
Returns TRUE if the current query is a < tt > SELECT< / tt > statement;
otherwise returns FALSE.
< h3 class = fn > bool < a name = "isValid" > < / a > TQSqlQuery::isValid () const
< / h3 >
Returns TRUE if the query is currently positioned on a valid
record; otherwise returns FALSE.
< h3 class = fn > bool < a name = "last" > < / a > TQSqlQuery::last ()< tt > [virtual]< / tt >
< / h3 >
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 < a href = "#isSelect" > isSelect< / a > () 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.
< p > < p > See also < a href = "#next" > next< / a > (), < a href = "#prev" > prev< / a > (), < a href = "#first" > first< / a > (), < a href = "#seek" > seek< / a > (), < a href = "#at" > at< / a > (), < a href = "#isActive" > isActive< / a > (), and < a href = "#isValid" > isValid< / a > ().
< p > Example: < a href = "sql.html#x2172" > sql/overview/navigating/main.cpp< / a > .
< h3 class = fn > < a href = "ntqsqlerror.html" > TQSqlError< / a > < a name = "lastError" > < / a > TQSqlQuery::lastError () const
< / h3 >
Returns error information about the last error (if any) that
occurred.
< p > < p > See also < a href = "ntqsqlerror.html" > TQSqlError< / a > .
< h3 class = fn > < a href = "ntqstring.html" > TQString< / a > < a name = "lastQuery" > < / a > TQSqlQuery::lastQuery () const
< / h3 >
Returns the text of the current query being used, or < a href = "ntqstring.html#TQString-null" > TQString::null< / a >
if there is no current query text.
< p > < p > See also < a href = "#executedQuery" > executedQuery< / a > ().
< h3 class = fn > bool < a name = "next" > < / a > TQSqlQuery::next ()< tt > [virtual]< / tt >
< / h3 >
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 < a href = "#isSelect" > isSelect< / a > () must return TRUE before
calling this function or it will do nothing and return FALSE.
< p > The following rules apply:
< p > < ul >
< li > 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.
< p > < li > If the result is currently located after the last record,
there is no change and FALSE is returned.
< p > < li > If the result is located somewhere in the middle, an attempt
is made to retrieve the next record.
< / ul >
< p > 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.
< p > < p > See also < a href = "#prev" > prev< / a > (), < a href = "#first" > first< / a > (), < a href = "#last" > last< / a > (), < a href = "#seek" > seek< / a > (), < a href = "#at" > at< / a > (), < a href = "#isActive" > isActive< / a > (), and < a href = "#isValid" > isValid< / a > ().
< p > Examples: < a href = "sql.html#x2159" > sql/overview/basicbrowsing/main.cpp< / a > , < a href = "sql.html#x2163" > sql/overview/basicbrowsing2/main.cpp< / a > , < a href = "sql.html#x2208" > sql/overview/delete/main.cpp< / a > , < a href = "sql.html#x2183" > sql/overview/order1/main.cpp< / a > , < a href = "sql.html#x2176" > sql/overview/retrieve1/main.cpp< / a > , < a href = "sql.html#x2265" > sql/overview/subclass4/main.cpp< / a > , and < a href = "sql.html#x2268" > sql/overview/subclass5/main.cpp< / a > .
< h3 class = fn > int < a name = "numRowsAffected" > < / a > TQSqlQuery::numRowsAffected () const
< / h3 >
Returns the number of rows affected by the result's SQL statement,
or -1 if it cannot be determined. Note that for < tt > SELECT< / tt >
statements, the value is undefined; see < a href = "#size" > size< / a > () instead. If the
query is not active (< a href = "#isActive" > isActive< / a > () returns FALSE), -1 is returned.
< p > < p > See also < a href = "#size" > size< / a > () and < a href = "ntqsqldriver.html#hasFeature" > TQSqlDriver::hasFeature< / a > ().
< p > Examples: < a href = "sql.html#x2164" > sql/overview/basicbrowsing2/main.cpp< / a > and < a href = "sql.html#x2168" > sql/overview/basicdatamanip/main.cpp< / a > .
< h3 class = fn > < a href = "ntqsqlquery.html" > TQSqlQuery< / a > & < a name = "operator-eq" > < / a > TQSqlQuery::operator= ( const < a href = "ntqsqlquery.html" > TQSqlQuery< / a > & other )
< / h3 >
Assigns < em > other< / em > to the query.
< h3 class = fn > bool < a name = "prepare" > < / a > TQSqlQuery::prepare ( const < a href = "ntqstring.html" > TQString< / a > & query )
< / h3 >
Prepares the SQL query < em > query< / em > for execution. The query may
contain placeholders for binding values. Both Oracle style
colon-name (e.g. < tt > :surname< / tt > ), and ODBC style (e.g. < tt > ?< / tt > )
placeholders are supported; but they cannot be mixed in the same
query. See the < a href = "#details" > Description< / a > for examples.
< p > < p > See also < a href = "#exec" > exec< / a > (), < a href = "#bindValue" > bindValue< / a > (), and < a href = "#addBindValue" > addBindValue< / a > ().
< h3 class = fn > bool < a name = "prev" > < / a > TQSqlQuery::prev ()< tt > [virtual]< / tt >
< / h3 >
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 < a href = "#isSelect" > isSelect< / a > () must return TRUE before
calling this function or it will do nothing and return FALSE.
< p > The following rules apply:
< p > < ul >
< li > If the result is currently located before the first record,
there is no change and FALSE is returned.
< p > < li > If the result is currently located after the last record, an
attempt is made to retrieve the last record.
< p > < li > If the result is somewhere in the middle, an attempt is made
to retrieve the previous record.
< / ul >
< p > 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.
< p > < p > See also < a href = "#next" > next< / a > (), < a href = "#first" > first< / a > (), < a href = "#last" > last< / a > (), < a href = "#seek" > seek< / a > (), < a href = "#at" > at< / a > (), < a href = "#isActive" > isActive< / a > (), and < a href = "#isValid" > isValid< / a > ().
< h3 class = fn > const < a href = "ntqsqlresult.html" > TQSqlResult< / a > * < a name = "result" > < / a > TQSqlQuery::result () const
< / h3 >
Returns the result associated with the query.
< h3 class = fn > bool < a name = "seek" > < / a > TQSqlQuery::seek ( int i, bool relative = FALSE )< tt > [virtual]< / tt >
< / h3 >
Retrieves the record at position (offset) < em > i< / em > , 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
< a href = "#isSelect" > isSelect< / a > () must return TRUE before calling this function.
< p > If < em > relative< / em > is FALSE (the default), the following rules apply:
< p > < ul >
< li > If < em > i< / em > is negative, the result is positioned before the
first record and FALSE is returned.
< li > Otherwise, an attempt is made to move to the record at position
< em > i< / em > . If the record at position < em > i< / em > 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.
< / ul >
< p > If < em > relative< / em > is TRUE, the following rules apply:
< p > < ul >
< li > If the result is currently positioned before the first
record or on the first record, and < em > i< / em > is negative, there is no
change, and FALSE is returned.
< li > If the result is currently located after the last record, and
< em > i< / em > is positive, there is no change, and FALSE is returned.
< li > If the result is currently located somewhere in the middle,
and the relative offset < em > i< / em > moves the result below zero, the
result is positioned before the first record and FALSE is
returned.
< li > Otherwise, an attempt is made to move to the record < em > i< / em >
records ahead of the current record (or < em > i< / em > records behind the
current record if < em > i< / em > is negative). If the record at offset < em > i< / em >
could not be retrieved, the result is positioned after the last
record if < em > i< / em > >= 0, (or before the first record if < em > i< / em > is
negative), and FALSE is returned. If the record is successfully
retrieved, TRUE is returned.
< / ul >
< p > < p > See also < a href = "#next" > next< / a > (), < a href = "#prev" > prev< / a > (), < a href = "#first" > first< / a > (), < a href = "#last" > last< / a > (), < a href = "#at" > at< / a > (), < a href = "#isActive" > isActive< / a > (), and < a href = "#isValid" > isValid< / a > ().
< p > Example: < a href = "sql.html#x2173" > sql/overview/navigating/main.cpp< / a > .
< h3 class = fn > void < a name = "setForwardOnly" > < / a > TQSqlQuery::setForwardOnly ( bool forward )
< / h3 >
Sets forward only mode to < em > forward< / em > . If forward is TRUE only
< a href = "#next" > next< / a > (), and < a href = "#seek" > seek< / a > () with positive values, are allowed for
navigating the results. Forward only mode needs far less memory
since results do not need to be cached.
< p > Forward only mode is off by default.
< p > Forward only mode cannot be used with data aware widgets like
< a href = "ntqdatatable.html" > TQDataTable< / a > , since they must to be able to scroll backward as well
as forward.
< p > < p > See also < a href = "#isForwardOnly" > isForwardOnly< / a > (), < a href = "#next" > next< / a > (), and < a href = "#seek" > seek< / a > ().
< h3 class = fn > int < a name = "size" > < / a > TQSqlQuery::size () const
< / h3 >
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-< tt > SELECT< / tt > statements (< a href = "#isSelect" > isSelect< / a > () returns FALSE), < a href = "#size" > size< / a > () will
return -1. If the query is not active (< a href = "#isActive" > isActive< / a > () returns FALSE),
-1 is returned.
< p > To determine the number of rows affected by a non-SELECT
statement, use < a href = "#numRowsAffected" > numRowsAffected< / a > ().
< p > < p > See also < a href = "#isActive" > isActive< / a > (), < a href = "#numRowsAffected" > numRowsAffected< / a > (), and < a href = "ntqsqldriver.html#hasFeature" > TQSqlDriver::hasFeature< / a > ().
< p > Example: < a href = "sql.html#x2174" > sql/overview/navigating/main.cpp< / a > .
< h3 class = fn > < a href = "ntqvariant.html" > TQVariant< / a > < a name = "value" > < / a > TQSqlQuery::value ( int i ) const< tt > [virtual]< / tt >
< / h3 >
Returns the value of the < em > i< / em > -th field in the query (zero based).
< p > The fields are numbered from left to right using the text of the
< tt > SELECT< / tt > statement, e.g. in < tt > SELECT forename, surname FROM people< / tt > ,
field 0 is < tt > forename< / tt > and field 1 is < tt > surname< / tt > . Using < tt > SELECT *< / tt >
is not recommended because the order of the fields in the query is
undefined.
< p > An invalid < a href = "ntqvariant.html" > TQVariant< / a > is returned if field < em > i< / em > does not exist, if
the query is inactive, or if the query is positioned on an invalid
record.
< p > < p > See also < a href = "#prev" > prev< / a > (), < a href = "#next" > next< / a > (), < a href = "#first" > first< / a > (), < a href = "#last" > last< / a > (), < a href = "#seek" > seek< / a > (), < a href = "#isActive" > isActive< / a > (), and < a href = "#isValid" > isValid< / a > ().
< p > Examples: < a href = "sql.html#x2160" > sql/overview/basicbrowsing/main.cpp< / a > , < a href = "sql.html#x2165" > sql/overview/basicbrowsing2/main.cpp< / a > , < a href = "sql.html#x2177" > sql/overview/retrieve1/main.cpp< / a > , < a href = "sql.html#x2262" > sql/overview/subclass3/main.cpp< / a > , < a href = "sql.html#x2266" > sql/overview/subclass4/main.cpp< / a > , < a href = "sql.html#x2269" > sql/overview/subclass5/main.cpp< / a > , and < a href = "sql.html#x2252" > sql/overview/table4/main.cpp< / a > .
<!-- eof -->
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< a href = "troll.html" > Trolltech< / a > < td align = center > < a href = "trademarks.html" > Trademarks< / a >
< td align = right > < div align = right > TQt 3.3.8< / div >
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