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能够连接各种数据库的API

                corrupt data is not read) 
                <LI>Read committed 
                <LI>Repeatable read 
                <LI>Serializable (the highest level, where 
                transactions are completely isolated from one another)</LI></UL>
            <P>SQLAPI++ maps different isolation levels on 
            <STRONG>ODBC</STRONG> server in the following way:</P>
            <P> <STRONG 
            >SA_ReadUncommitted</STRONG> =     
            SQL_TXN_READ_UNCOMMITTED<BR><STRONG> SA_ReadCommitted</STRONG> =   
             SQL_TXN_READ_COMMITTED<BR><STRONG> SA_RepeatableRead</STRONG> =    
            SQL_TXN_REPEATABLE_READ<BR><STRONG> SA_Serializable</STRONG> =   
            SQL_TXN_SERIALIZABLE</P>
            <P>For more details see <A 
            href="../OnLineDoc/Connection_setIsolationLevel.html">SAConnection::setIsolationLevel</A>.</P>
            <P>&nbsp;</P>
            
            <H3><A 
            name="Working with Long or Lob(CLob, BLob) data">Working with Long or Lob(CLob, 
            BLob) data</A>    </H3>
            <P> 
            SQLAPI++ supports four types for working with 
            Long or Lob(CLob, BLob) data:</P>
            <P>
            <TABLE border=1 cellPadding=1 cellSpacing=1 style="WIDTH: 100%" 
            width=100%>
                
                <TR bgColor=navy>
                    <TD><FONT color=white 
                        style="BACKGROUND-COLOR: #000080">Name</FONT></TD>
                    <TD><FONT color=white 
                        style="BACKGROUND-COLOR: #000080">C 
                        enum constant</FONT></TD>
                </TR>
                <TR>
                    <TD>LongBinary</TD>
                    <TD>SA_dtLongBinary</TD>
                </TR>
                <TR>
                    <TD>LongChar</TD>
                    <TD>SA_dtLongChar</TD>
                </TR>
                <TR>
                    <TD>BLob (Binary Large object)</TD>
                    <TD>SA_dtBLob</TD>
                </TR>
                <TR>
                    <TD>CLob (Character Large object)</TD>
                    <TD>SA_dtCLob</TD>
                </TR></TABLE></P>
            <P>SQLAPI++ maps data types to 
            <STRONG>ODBC</STRONG> constants. Actual mapping from constant to SQL 
            type is <STRONG>ODBC</STRONG> driver specific. The table below shows 
            how SQLAPI++ data types correspond with <STRONG>ODBC</STRONG>       
                            
                  constants:</P>
            <P><EM>SA_dtLongBinary</EM> 
            &lt;=    &gt; SQL_LONGVARBINARY<BR><EM>SA_dtLongChar</EM> 
            &lt;=  
              &gt; SQL_LONGVARCHAR<BR 
            ><EM>SA_dtBLob</EM> =    &gt; 
            SQL_LONGVARBINARY<BR><EM>SA_dtCLob 
            </EM>=&gt; 
            SQL_LONGVARCHAR</EM></P>
            <P>
            For more details see <A href="../HowTo/blobs.html">How To - Working with Long or Lob(CLob, BLob) data</A></P>
            <P>&nbsp;</P>
            
            <H3><A 
            name="Returning output parameters">Returning output 
            parameters</A>  </H3>
            <P>       
                       
             In <STRONG>ODBC</STRONG> 
            processing output parameters depends on a 
            driver.</P>
            <P>  
                       
             If DBMS allows to return output parameters 
            then SQLAPI++ stores the returned values of output parameters in the 
            <A href="../OnLineDoc/Param.html" >SAParam</A>
            objects bound to those 
            parameters. On some servers these returned values are not guaranteed 
            to be set until all results returned by the procedure have been 
            fetched (using <A href="../OnLineDoc/Command_FetchNext.html" >SACommand::FetchNext</A> 
            method).</P>
            <P>       
                       
             See ODBC driver documentation on output 
            parameters availability on different   
            DBMSs.</P>
            <P>SQLAPI++ Library automatically creates <A href="../OnLineDoc/Param.html" >SAParam</A>
            object to represent procedure 
            status return code or function return value (if any). You can refer 
            to this <A href="../OnLineDoc/Param.html" >SAParam</A> 
            object using SQLAPI++ predefined 
            name <STRONG>&quot;RETURN_VALUE&quot;</STRONG>. 
            </P>
            <P>For more details see <A 
            href="../OnLineDoc/Command_Execute.html" >SACommand::Execute</A>, 
            <A href="../OnLineDoc/Param_Usage.html" >SAParam 
            object</A>, <A 
            href="../HowTo/return_param.html" >How To - Returning Output Parameters</A>.</P>
            <P>&nbsp;</P>
            
            <H3><A name="Cancelling queries">Cancelling 
            queries</A> </H3>
            <P>
            Using 
            <A href="../OnLineDoc/Command_Cancel.html" >SACommand::Cancel</A> 
            method you 
            can cancel the following types of processing on a statement:
			</P>
                <UL type=disc>
                <LI>A function running asynchronously on the 
                statement.<BR>
                <LI>
                A function running on the statement on 
				another thread.</LI></UL>    
            <p>   
             SQLAPI++ calls <STRONG>SQLCancel</STRONG> 
             function to cancel a query. To get more 
             details see <STRONG>SQLCancel</STRONG> function 
            description in <STRONG>ODBC</STRONG> 
                 documentation.
            </p>
            <P>For more details see <A 
            href="../OnLineDoc/Command_Cancel.html" > 
            SACommand::Cancel</A>.</P>
            <P>&nbsp;</P>
            
            <H3><A 
            name="Connection and command options">Connection, command, parameter and field 
            options</A>   </H3>
            <P>A server specific option can relate to a 
            connection, command,&nbsp; parameter or field. We recommend you 
            specify each option in an appropriate object, although it is 
            possible to specify them in the parental object as well. In that 
            case the option affects all the child objects. </P>
            <P>A connection related option must be specified 
            in a&nbsp; <A href="../OnLineDoc/Connection.html">SAConnection</A> 
            object. </P>
            <P>A command related option may be specified in 
            either <A href="../OnLineDoc/Connection.html">SAConnection</A> 
            object or <A href="../OnLineDoc/Command.html">SACommand</A> 
            object. If it is specified 
            in <A href="../OnLineDoc/Connection.html">SAConnection</A> 
            object it affects all 
            the commands on that connection. </P>
            <P>A parameter related option may be specified in 
            <A href="../OnLineDoc/Connection.html">SAConnection</A> 
            object, <A href="../OnLineDoc/Command.html">SACommand</A> 
            object or <A href="../OnLineDoc/Param.html">SAParam</A> 
            object. If it is specified in <A href="../OnLineDoc/Connection.html">SAConnection</A> 
            object it affects all 
            the commands and therefore all the parameters on that connection. If 
            it is specified in <A href="../OnLineDoc/Command.html">SACommand</A> 
            object it affects all the 
            parameters on that command. </P>
            <P>A field related option may be specified in 
            <A href="../OnLineDoc/Connection.html">SAConnection</A> 
            object, <A href="../OnLineDoc/Command.html">SACommand</A> 
            object or <A href="../OnLineDoc/Field.html">SAField</A> 
            object. If it is specified in <A href="../OnLineDoc/Connection.html">SAConnection</A> 
            object it affects all 
            the commands and therefore all the fields on that connection. If it 
            is specified in <A href="../OnLineDoc/Command.html">SACommand</A> 
            object it affects all the 
            fields on that command. </P>
            <P>       Specific 
            options for <STRONG>ODBC</STRONG>:</P>
            <TABLE border=1 cellPadding=5 width=100%>
                <TBODY>
                <TR bgColor=#000094>
                    <TD width=17%>
                        <P><STRONG><FONT color=white face="">Option name / Scope</FONT>&nbsp; 
                        </STRONG></P></TD>
                    <TD>
                        <P><STRONG><FONT color=white face=""> Description</FONT> 
                        </STRONG></P></TD></TR>
               <TR>
                    <TD><STRONG>
                        <P align=center>
                        <STRONG>UseManagerOnUNIX</STRONG> 
                        </P>
                        <P align=center>
                        <STRONG></STRONG></STRONG>Connection 
                        related. Should be specified before the first connection 
                        is made.&nbsp;&nbsp;</P> 
                        </TD>
                    <TD>
                        <P>     
                              Forces SQLAPI++     
                              Library to use specified 
                        library on UNIX.
                        <BR >   
                             </P>
                        <P><EM>Valid values</EM>
                     : 
                        &quot;&lt;name of
                    library you 
                        want to use&gt;&quot;.
                    <BR><EM>Default value</EM>: &quot;libiodbc.so.2&quot;.</P></TD>
               </TR>
                <TR>
                    <TD><STRONG>
                        <P align=center><STRONG>PreFetchRows</STRONG></P></STRONG>
                        <P align=center>Command related. 
                        Should be specified before command execution.<STRONG><STRONG></STRONG></STRONG></P></TD>
                    <TD>
                        <P>Forces SQLAPI++ Library to fetch 
                        rows in bulk, rather than retrieving records one by 
                        one.</P>
                        <P><EM>Valid values</EM>: String containing number of rows in the fetch 
                        buffer. <BR><EM>Default value</EM>: 
                        &quot;1&quot;.</P></TD>