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<meta NAME="Author" CONTENT="Stefan Tchekanov">
<meta Name="description" Content="CODBCRecordset class">
<meta Name="keywords" Content="MFC C++ Database">
<title>CODBCRecordset class</title>
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<body bgcolor="#ffffff" text="#000000">
<h3 align="center"><font COLOR="#000000">CODBCRecordset class</font></h3>
<p align="center">CODBCRecordset class is intended to be full replacement of all
ClassWizard generated CRecordset derived classes in MFC projects. </p>
<hr>
<!-- Author and contact details -->
<p>This article was contributed by <a href="mailto:stefant@iname.com">Stefan Tchekanov</a>.<br>
Platform: VC 5.0 & VC 6.0
<ul>
<li><a href="##intro">Introduction</a> </li>
<li><a href="##examples">Examples of how to use </a><a href="##how_works">CODBCRecordset</a>
</li>
<li><a href="##how_works">How does CODBCRecordset work?</a> </li>
</ul>
<p> </p>
<p><a name="#intro"></a><big><strong>Introduction</strong></big></p>
<p>In a usual MFC database project we have a lot of CRecordset derived classes generated
by ClassWizrad. The presented here CODBCRecordset class is a very easy to use replacement
of all these CRecordset classes. CODBCRecordset is derived from CRecordset but it does not
have hardcoded inside the number and the type of the database fields.</p>
<p>I have seen some implementations trying to solve this problem. But CODBCRecordset has
at least two advantages:
<ol>
<li>CODBCRecordset can be used not only to get values from the database, but to write values
into the database too using the MFC way.</li>
<li>The other implementations canot open simultaneously more than one recordset trough one
database connection when the database is MS SQL Server. In some cases this could be very
big problem because opening a new connection is time and resources expensive.</li>
</ol>
<p>Because CODBCRecordset is derived from CRecordset and uses its data exchange mechanism
it is fully compatible with MFC ODBC class CDatabase.</p>
<p>Each field value is stored in a CDBField object. CDBField class is inherited from
CDBVariant and has added some extra functionality to be easy to use.</p>
<p>CODBCRecordset and CDBField classes support all database data types. CDBField makes
implicit type conversion where is appropriate to supply the data in the requested format.</p>
<p>Here is a list of CODBCRecordset and CDBField methods:</p>
<table border="1" width="100%" cellspacing="0">
<tr>
<td colspan="2" align="center" bgcolor="#C0C0C0"><a name="#class_rset"></a><strong>CODBCRecordset
class</strong></td>
</tr>
<tr>
<td width="32%">Constructor</td>
<td width="68%">The same as for CRecordset accepting CDatabase*</td>
</tr>
<tr>
<td width="32%">BOOL Open( LPCTSTR lpszSQL,<br>
UINT nOpenType,<br>
DWORD dwOptions );</td>
<td width="68%">Open the recordset<br>
<strong>lpszSQL</strong> is a SQL statement that returns recordset<br>
e.g. SELECT * FROM tablename<br>
<strong>nOpenType</strong> is CRecordset open type, see CRecordset::Open()<br>
<strong>dwOptions</strong> is CRecordset options, see CRecordset::Open()<p>Note that
lpszSQL and nOpenType have exchanged their positions compared to CRecordset::Open()</td>
</tr>
<tr>
<td width="32%">short GetODBCFieldCount()</td>
<td width="68%">Returns number of the fields (columns) in the recordset. This method is
defined in CRecordset.</td>
</tr>
<tr>
<td width="32%">int
GetFieldID( LPCTSTR )</td>
<td width="68%">Returns a field index by given field name. It is case insensitive.
CRecordset::GetFieldIndexByName() works, but is case sensitive.</td>
</tr>
<tr>
<td width="32%">CString GetFieldName( int )</td>
<td width="68%">Returns a field name by given field index</td>
</tr>
<tr>
<td width="32%">CDBField& Field( LPCTSTR )<br>
CDBField& Field( int )</td>
<td width="68%">Through this method you can get a reference to the internal CDBField
object corresponding to the specified column (See the <a href="##class_dbfield">CDBField
class</a> table for details about CDBField).<p>There are two forms of the method - with
argument of type <strong>LPCTSTR szName</strong> - specifying the name of the column, and <strong>int
nID</strong> - specifying the index of the coulmn in the recordset.</p>
<p>These methods can be used as lvalue in expressions. Thus you can write values to the
database.</td>
</tr>
<tr>
<td width="32%">CDBField& operator( LPCTSTR )<br>
CDBField& operator( int )</td>
<td width="68%">The function operator is defined for easy of use of the class and just
calls the corresponding Field() method<p>There are two forms of the function operator -
with argument of type <strong>LPCTSTR szName</strong> - specifying the name of the column,
and <strong>int nID</strong> - specifying the index of the coulmn in the recordset.</p>
<p>These can be used as lvalue in expressions. Thus you can write values to the database.</td>
</tr>
<tr>
<td width="32%"><table border="0" width="100%" cellspacing="0" cellpadding="0">
<tr>
<td width="50%">bool</td>
<td width="50%">GetBool()</td>
</tr>
<tr>
<td width="50%">unsigned char</td>
<td width="50%">GetChar()</td>
</tr>
<tr>
<td width="50%">short</td>
<td width="50%">GetShort()</td>
</tr>
<tr>
<td width="50%">int</td>
<td width="50%">GetInt()</td>
</tr>
<tr>
<td width="50%">long</td>
<td width="50%">GetLong()</td>
</tr>
<tr>
<td width="50%">float</td>
<td width="50%">Getfloat()</td>
</tr>
<tr>
<td width="50%">double</td>
<td width="50%">GetDouble()</td>
</tr>
<tr>
<td width="50%">COleDateTime</td>
<td width="50%">GetDate()</td>
</tr>
<tr>
<td width="50%">CString</td>
<td width="50%">GetString()</td>
</tr>
<tr>
<td width="50%">CLongBinary*</td>
<td width="50%">GetBinary()</td>
</tr>
</table>
</td>
<td width="68%">All of these methods do the appropriate type conversions depending on
their return value and the type of the underlying data in the database.<p>These methods
just call Field().AsXXX()<br>
(See the <a href="##class_dbfield">CDBField class</a> table for details about CDBField).</p>
<p>There are two forms of these methods - with argument of type <strong>LPCTSTR szName</strong>
- specifying the name of the column, and <strong>int nID</strong> - specifying the index
of the coulmn in the recordset.</p>
<p>These cannot be used as lvalue in expressions.</td>
</tr>
</table>
<p> </p>
<table border="1" width="100%" cellspacing="0">
<tr>
<td width="32%" colspan="2" align="center" bgcolor="#C0C0C0"><a name="#class_dbfield"></a><strong>CDBField
class</strong></td>
</tr>
<tr>
<td width="32%">Constructors</td>
<td width="68%">No public constructors. CDBField cannot be instantiated except by
CODBCRecordset to be used in internal structures to support data exchange. These objects
are accessible through CODBCRecordset methods.</td>
</tr>
<tr>
<td width="32%"><table border="0" width="100%" cellspacing="0" cellpadding="0">
<tr>
<td width="50%">bool</td>
<td width="50%">AsBool()</td>
</tr>
<tr>
<td width="50%">unsigned char</td>
<td width="50%">AsChar()</td>
</tr>
<tr>
<td width="50%">short</td>
<td width="50%">AsShort()</td>
</tr>
<tr>
<td width="50%">int</td>
<td width="50%">AsInt()</td>
</tr>
<tr>
<td width="50%">long</td>
<td width="50%">AsLong()</td>
</tr>
<tr>
<td width="50%">float</td>
<td width="50%">AsFloat()</td>
</tr>
<tr>
<td width="50%">double</td>
<td width="50%">AsDoble()</td>
</tr>
<tr>
<td width="50%">COleDateTime</td>
<td width="50%">AsDate()</td>
</tr>
<tr>
<td width="50%">CString</td>
<td width="50%">AsString()</td>
</tr>
<tr>
<td width="50%">CLongBinary*</td>
<td width="50%">AsBinary()</td>
</tr>
</table>
</td>
<td width="68%">All of these methods do the appropriate type conversions depending on
their return value and the type of the underlying data in the database (See the <a
href="##conv_asxxx">AsXXX methods</a> table for data conversion rules).<p>There is no data
type <em>Int</em> but <strong>AsInt()</strong> is equal to <strong>AsLong()</strong></td>
</tr>
<tr>
<td width="32%">assignment operators</td>
<td width="68%">There are defined assignment operators accepting <strong>boo</strong>l, <strong>unsigned
char</strong>, <strong>short</strong>, <strong>int</strong>, <strong>long</strong>, <strong>COleDateTime</strong>
and <strong>CString</strong>. So CDBField objects can be lvalues. There is no assignemt
operator accepting CLongBinary because MFC does not support writing CLongBinary values
into database. These assignment operators do appropriate conversions to the underlying
database column data type except CLongBinary (See the <a href="##conv_assign">assignment
operators</a> table for data conversion rules).</td>
</tr>
<tr>
<td width="32%">const CString& GetName()</td>
<td width="68%">Returns the field name this object corresponds to.</td>
</tr>
<tr>
<td width="32%"><table border="0" width="100%" cellspacing="0" cellpadding="0">
<tr>
<td width="50%">bool</td>
<td width="50%">IsNull()</td>
</tr>
<tr>
<td width="50%">bool</td>
<td width="50%">IsBool()</td>
</tr>
<tr>
<td width="50%">bool</td>
<td width="50%">IsChar()</td>
</tr>
<tr>
<td width="50%">bool</td>
<td width="50%">IsShort()</td>
</tr>
<tr>
<td width="50%">bool</td>
<td width="50%">IsInt()</td>
</tr>
<tr>
<td width="50%">bool</td>
<td width="50%">IsLong()</td>
</tr>
<tr>
<td width="50%">bool</td>
<td width="50%">IsFloat()</td>
</tr>
<tr>
<td width="50%">bool</td>
<td width="50%">IsDouble()</td>
</tr>
<tr>
<td width="50%">bool</td>
<td width="50%">IsNumber()</td>
</tr>
<tr>
<td width="50%">bool</td>
<td width="50%">IsDate()</td>
</tr>
<tr>
<td width="50%">bool</td>
<td width="50%">IsString()</td>
</tr>
<tr>
<td width="50%">bool</td>
<td width="50%">IsBinary()</td>
</tr>
</table>
</td>
<td width="68%">Each of these return true if the field contains a value of the
corresponding data type.<br>
<p>There is no data type <em>Number</em> but <strong>IsNumber()</strong> returns true if <strong>IsShort()
|| IsLong() || IsFloat() || IsDouble()</strong>.</p>
<p>There is no data type <em>Int</em> but <strong>IsInt()</strong> returns true if <strong>IsLong()</strong>
returns true.</td>
</tr>
</table>
<p> </p>
<table border="1" width="100%" cellspacing="0" cellpadding="2">
<tr>
<td colspan="11" bgcolor="#C0C0C0"><p align="center"><a name="#conv_asxxx"></a><strong>Conversions
made by AsXXX methods</strong></td>
</tr>
<tr>
<td bgcolor="#800000"> </td>
<td colspan="10" bgcolor="#008000"><p align="center"><font color="#FFFFFF"><strong>Values
in the database</strong></font></td>
</tr>
<tr>
<td width="10%" bgcolor="#800000"> </td>
<td width="10%" align="center" bgcolor="#008000"><font color="#FFFFFF"><strong>NULL</strong></font></td>
<td width="10%" align="center" bgcolor="#008000"><font color="#FFFFFF"><strong>BOOL</strong></font></td>
<td width="10%" align="center" bgcolor="#008000"><font color="#FFFFFF"><strong>UCHAR</strong></font></td>
<td width="10%" align="center" bgcolor="#008000"><font color="#FFFFFF"><strong>SHORT</strong></font></td>
<td width="10%" align="center" bgcolor="#008000"><font color="#FFFFFF"><strong>LONG</strong></font></td>
<td width="10%" align="center" bgcolor="#008000"><font color="#FFFFFF"><strong>SINGLE</strong></font></td>
<td width="10%" align="center" bgcolor="#008000"><font color="#FFFFFF"><strong>DOUBLE</strong></font></td>
<td width="10%" align="center" bgcolor="#008000"><font color="#FFFFFF"><strong>DATE</strong></font></td>
<td width="10%" align="center" bgcolor="#008000"><font color="#FFFFFF"><strong>STRING</strong></font></td>
<td width="10%" align="center" bgcolor="#008000"><font color="#FFFFFF"><strong>BINARY</strong></font></td>
</tr>
<tr>
<td width="10%" bgcolor="#800000"><font color="#FFFFFF"><strong>AsBool</strong></font></td>
<td width="10%">false</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%"> </td>
<td width="10%">*</td>
<td width="10%"> </td>
</tr>
<tr>
<td width="10%" bgcolor="#800000"><font color="#FFFFFF"><strong>AsChar</strong></font></td>
<td width="10%">0x32</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%"> </td>
<td width="10%">*</td>
<td width="10%"> </td>
</tr>
<tr>
<td width="10%" bgcolor="#800000"><font color="#FFFFFF"><strong>AsShort</strong></font></td>
<td width="10%">0</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%"> </td>
<td width="10%">*</td>
<td width="10%"> </td>
</tr>
<tr>
<td width="10%" bgcolor="#800000"><font color="#FFFFFF"><strong>AsInt</strong></font></td>
<td width="10%">0</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%"> </td>
<td width="10%">*</td>
<td width="10%"> </td>
</tr>
<tr>
<td width="10%" bgcolor="#800000"><font color="#FFFFFF"><strong>AsLong</strong></font></td>
<td width="10%">0</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%"> </td>
<td width="10%">*</td>
<td width="10%"> </td>
</tr>
<tr>
<td width="10%" bgcolor="#800000"><font color="#FFFFFF"><strong>AsFloat</strong></font></td>
<td width="10%">0.0</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%"> </td>
<td width="10%">*</td>
<td width="10%"> </td>
</tr>
<tr>
<td width="10%" bgcolor="#800000"><font color="#FFFFFF"><strong>AsDouble</strong></font></td>
<td width="10%">0.0</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%"> </td>
<td width="10%">*</td>
<td width="10%"> </td>
</tr>
<tr>
<td width="10%" bgcolor="#800000"><font color="#FFFFFF"><strong>AsDate</strong></font></td>
<td width="10%">null</td>
<td width="10%">invalid</td>
<td width="10%">invalid</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%"> </td>
</tr>
<tr>
<td width="10%" bgcolor="#800000"><font color="#FFFFFF"><strong>AsString</strong></font></td>
<td width="10%">empty</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
<td width="10%">*</td>
</tr>
<tr>
<td width="10%" bgcolor="#800000"><font color="#FFFFFF"><strong>AsLongBinary</strong></font></td>
<td width="10%">NULL</td>
<td width="10%"> </td>
<td width="10%"> </td>
<td width="10%"> </td>
<td width="10%"> </td>
<td width="10%"> </td>
<td width="10%"> </td>
<td width="10%"> </td>
<td width="10%"> </td>
<td width="10%">*</td>
</tr>
<tr>
<td colspan="11">Empty cells indicate the conversion <strong>is not</strong> available,
thus code asserts.<br>
Cells marked with * indicate conversion <strong>is</strong> available (See the <a
href="##conv_alg">Conversion algorithms</a> table for data conversion rules).</td>
</tr>
</table>
<p> </p>
<table border="1" width="100%" cellspacing="0" cellpadding="2">
<tr>
<td width="100%" colspan="10" bgcolor="#C0C0C0"><p align="center"><a name="#conv_assign"></a><strong>Conversions
made by assignment operators</strong></td>
</tr>
<tr>
<td width="11%" bgcolor="#800000"><font color="#FFFFFF"><strong>Database Field Type</strong></font></td>
<td width="89%" colspan="9" bgcolor="#008000"><p align="center"><font color="#FFFFFF"><strong>Argument
of the assignment operator</strong></font></td>
</tr>
<tr>
<td width="11%" bgcolor="#800000"> </td>
<td width="11%" align="center" bgcolor="#008000"><font color="#FFFFFF"><strong>bool</strong></font></td>
<td width="11%" align="center" bgcolor="#008000"><font color="#FFFFFF"><strong>unsigned
char</strong></font></td>
<td width="11%" align="center" bgcolor="#008000"><font color="#FFFFFF"><strong>short</strong></font></td>
<td width="11%" align="center" bgcolor="#008000"><font color="#FFFFFF"><strong>int</strong></font></td>
<td width="11%" align="center" bgcolor="#008000"><font color="#FFFFFF"><strong>long</strong></font></td>
<td width="11%" align="center" bgcolor="#008000"><font color="#FFFFFF"><strong>float</strong></font></td>
<td width="11%" align="center" bgcolor="#008000"><font color="#FFFFFF"><strong>double</strong></font></td>
<td width="11%" align="center" bgcolor="#008000"><font color="#FFFFFF"><strong>COleDateTime</strong></font></td>
<td width="12%" align="center" bgcolor="#008000"><font color="#FFFFFF"><strong>String</strong></font></td>
</tr>
<tr>
<td width="11%" bgcolor="#800000"><font color="#FFFFFF"><strong>NULL</strong></font></td>
<td width="11%"> </td>
<td width="11%"> </td>
<td width="11%"> </td>
<td width="11%"> </td>
<td width="11%"> </td>
<td width="11%"> </td>
<td width="11%"> </td>
<td width="12%"> </td>
<td width="12%"> </td>
</tr>
<tr>
<td width="11%" bgcolor="#800000"><font color="#FFFFFF"><strong>BOOL</strong></font></td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="12%"> </td>
<td width="11%">*</td>
</tr>
<tr>
<td width="11%" bgcolor="#800000"><font color="#FFFFFF"><strong>UCHAR</strong></font></td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="12%"> </td>
<td width="11%">*</td>
</tr>
<tr>
<td width="11%" bgcolor="#800000"><font color="#FFFFFF"><strong>SHORT</strong></font></td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="12%"> </td>
<td width="11%">*</td>
</tr>
<tr>
<td width="11%" bgcolor="#800000"><font color="#FFFFFF"><strong>LONG</strong></font></td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="12%"> </td>
<td width="11%">*</td>
</tr>
<tr>
<td width="11%" bgcolor="#800000"><font color="#FFFFFF"><strong>SINGLE</strong></font></td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="12%"> </td>
<td width="11%">*</td>
</tr>
<tr>
<td width="11%" bgcolor="#800000"><font color="#FFFFFF"><strong>DOUBLE</strong></font></td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="12%"> </td>
<td width="11%">*</td>
</tr>
<tr>
<td width="11%" bgcolor="#800000"><font color="#FFFFFF"><strong>DATE</strong></font></td>
<td width="11%"> </td>
<td width="11%"> </td>
<td width="11%"> </td>
<td width="11%"> </td>
<td width="11%"> </td>
<td width="11%"> </td>
<td width="11%"> </td>
<td width="12%">*</td>
<td width="11%">*</td>
</tr>
<tr>
<td width="11%" bgcolor="#800000"><font color="#FFFFFF"><strong>STRING</strong></font></td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="11%">*</td>
<td width="12%">*</td>
<td width="11%">*</td>
</tr>
<tr>
<td width="11%" bgcolor="#800000"><font color="#FFFFFF"><strong>BINARY</strong></font></td>
<td width="11%"> </td>
<td width="11%"> </td>
<td width="11%"> </td>
<td width="11%"> </td>
<td width="11%"> </td>
<td width="11%"> </td>
<td width="11%"> </td>
<td width="12%"> </td>
<td width="12%"> </td>
</tr>
<tr>
<td colspan="10">Empty cells indicate the conversion <strong>is not</strong> available,
thus code asserts.<br>
Cells marked with * indicate conversion <strong>is</strong> available (See the <a
href="##conv_alg">Conversion algorithms</a> table for data conversion rules).</td>
</tr>
</table>
<p> </p>
<table border="1" width="100%" cellspacing="0" cellpadding="2">
<tr>
<td width="100%" colspan="2" align="center" bgcolor="#C0C0C0"><a name="#conv_alg"></a><strong>Conversion
algorithms</strong></td>
</tr>
<tr>
<td width="22%">String to Bool</td>
<td width="78%">comparing the first character of the string with 'T'</td>
</tr>
<tr>
<td width="22%">Char to Bool</td>
<td width="78%">comparing the character with 'T'</td>
</tr>
<tr>
<td width="22%">Bool to String</td>
<td width="78%">String = (bVal) ? 'T' : 'F'</td>
</tr>
<tr>
<td width="22%">Bool to Char</td>
<td width="78%">Char = (bVal) ? 'T' : 'F'</td>
</tr>
<tr>
<td width="22%">String to Number</td>
<td width="78%">appropriate atoX() function</td>
</tr>
<tr>
<td width="22%">Number to String</td>
<td width="78%">CString::Format() method using the appropriate format specifier string</td>
</tr>
<tr>
<td width="22%">String to Date</td>
<td width="78%">COleDateTime::ParseDateTime() method</td>
</tr>
<tr>
<td width="22%">Date to String</td>
<td width="78%">COleDateTime::Format() method</td>
</tr>
</table>
<p> </p>
<p><a name="#examples"></a><big><strong>Examples of how to use CODBCRecordset</strong></big></p>
<p>You should include the files <font color="#800000">ODBCRecordset.h</font> and <font
color="#800000">ODBCRecordset.cpp</font> in your project.</p>
<p>I usually include this line in my <font color="#800000">StdAfx.h</font> file.</p>
<pre><tt><font color="#990000">#include "ODBCRecordset.h"</font></tt></pre>
<p>Here is a simple code showing how CODBCRecordset can be used.</p>
<pre><tt><font color="#990000">/////////////////////////////////////////////////////////////////////////////
CDatabase db;
// This connect string will pop up the ODBC connect dialog
CString cConnect = "ODBC;";
db.Open( NULL, // DSN
FALSE, // Exclusive
FALSE, // ReadOnly
cConnect, // ODBC Connect string
TRUE // Use cursor lib
);
COleDateTime dOrderDate;
CODBCRecordset rs( &db );
<strong>rs.Open( "SELECT * FROM Orders \
WHERE ORDER_DATE > 'jan 1 2000' \
ORDER BY ORDER_DATE" );
</strong>for( ; ! rs.IsEOF(); rs.MoveNext() )
{
// The choice is yours. You may choose whatever way
// you want to get the values
//
// These return COleDateTime value
dOrderDate = <strong>rs.GetDate( "ORDER_DATE" );</strong>
dOrderDate = <strong>rs.Field("ORDER_DATE").AsDate();</strong>
// These make implicit call to AsDate()
dOrderDate = <strong>rs("ORDER_DATE");</strong>
dOrderDate = <strong>rs.Field("ORDER_DATE");</strong>
// Now edit the fields in the recordset
rs.Edit();
<strong>rs("ORDER_DATE")</strong> = "jan 1 1999"; // Implicit conversion
<strong>rs.Field("ORDER_DATE")</strong> = "jan 1 1999"; // Implicit conversion
rs.Update();
} // for(....
/////////////////////////////////////////////////////////////////////////////
</font></tt></pre>
<p>If <strong>ORDER_DATE</strong> is stored in the database as <strong>datetime</strong>
or compatible data type the value will be get directly.<br>
If <strong>ORDER_DATE</strong> is stored in the database as <strong>string</strong> or
compatible data type (char, varchar) the value will be converted via
COleDateTime::ParseDateTime() method. If conversion fails, <strong>dOrderDate</strong>
will be set to <strong>COleDatetime::invalid</strong>.</p>
<p>When opening a resultset generated by join statements it is possible to get 2 or more
columns that have the same name. CODBCRecordset leaves the name of the first column intact
but other repeated columns are renamed with adding the number this columns repeats the
name. Not repeated column names are left intact. E.g.</p>
<p><tt><font color="#990000"><strong>SELECT * FROM Orders, Customers WHERE Orders.CUST_ID
= Customers.ID</strong></font></tt></p>
<p>If the table <em>Orders</em> have a column with name <em>ID</em> and <em>Customers</em>
have a column with name <em>ID</em>, CODBCRecordset will rename <em>ID</em> from Customers
to <strong>ID2</strong> and all other not repeating column names will be intact.</p>
<p>Well, here is a tip: Rename columns manualy to be sure what name they have, e.g.</p>
<p><tt><font color="#990000"><strong>SELECT Orders.*, Customers.ID as CUSTOMERS_ID <br>
FROM Orders, Customers <br>
WHERE Orders.CUST_ID = Customers.ID</strong></font></tt></p>
<p> </p>
<p><a name="#how_works"></a><big><strong>How does CODBCRecordset work?</strong></big></p>
<p>CODBCRecordset allocates storage for all fields in the resultset and uses MFC <em>Record
Field eXchange</em> mechanizm like it has been inherited from CRecordset using
ClassWizard.</p>
<p>That's all.</p>
<p><a href="ODBCRecordset.zip">Download source</a> ODBCRecordset.zip (13 KB)</p>
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Stefan does programming since his early ages more than 30 years ago. Later he began programming at his work and now he is very happy to work his hobby. He owns a Master's degree in Computer Science.
During his professional career, Stefan has worked with many technologies. His programming experience includes C/C++, Java, C#, PHP, JavaScript, MFC, ATL, ASP, ASP.NET, TCP/IP, SQL. He has worked with different operating systems: Windows, Linux, Mac OS X, iOS, Android, Solaris, FreeBSD, NetBSD and QNX.
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Stefan has a wife and 2 children. He likes in his spear time to travel with his family to see new and interesting places.
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