db2.html

能够连接各种数据库的API

            href="../HowTo/connect.html">How To - Connecting to databases</A>, <A 
            href="../OnLineDoc/Connection_Usage.html">SAConnection object</A>, <A 
            href="../OnLineDoc/Connection_Connect.html">SAConnection::Connect</A>.</P>
            <P>&nbsp;</P>
            
            <H3><A 
            name="Transaction isolation levels">Transaction isolation 
            levels</A>  </H3>
            <P>SQL-92 defines four isolation levels, all of 
            which are supported by SQLAPI++:</P>
            <UL>
                <LI>Read uncommitted (the lowest level where 
                transactions are isolated just enough to ensure that physically 
                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>DB2</STRONG> server in the following way:</P>
            <P> <STRONG 
            >SA_ReadUncommitted</STRONG> = SQL_TXN_READ_UNCOMMITTED 
  ('Uncommited 
            Read')<BR><STRONG> SA_ReadCommitted</STRONG> = 
            SQL_TXN_READ_COMMITTED  
            ('Cursor Stability')<BR><STRONG> SA_RepeatableRead</STRONG> = SQL_TXN_REPEATABLE_READ ('Repeatable  
            Read')<BR><STRONG> SA_Serializable</STRONG> = SQL_TXN_SERIALIZABLE  
            ('Read  
            Stability')</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>The table below shows how SQLAPI++ data 
            types correspond with servers original data types:</P>
            <P><EM>SA_dtLongBinary</EM> &lt;= &gt; LONG VARGRAPHIC<BR><EM>SA_dtLongChar</EM> 
            &lt;= &gt; LONG VARCHAR<BR 
            ><EM>SA_dtBLob</EM> = &gt; 
            BLOB<BR><EM>SA_dtCLob 
            </EM>=&gt; CLOB, DBCLOB</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>DB2</STRONG>
              output parameters are 
            available immediately after calling 
            <A 
            href="../OnLineDoc/Command_Execute.html">SACommand::Execute</A> 
            .</P>      
                         
                     
                <P>SQLAPI++ Library automatically creates 
                <A href="../OnLineDoc/Param.html" >SAParam</A>
                object to represent function 
            return value. 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>DB2</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> 
            DB2</STRONG>:</P> 
            <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>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></TR>
                <TR>
                    <TD><STRONG>
                        <P align=center>ReturnStatus</P></STRONG>
                        <P align=center>Command related. 
                        Should be specified before describing parameters or 
                        command execution.<STRONG></STRONG></P></TD>
                    <TD>
                        <P>DB2 stored procedures always return a value, and SQLAPI++ 
                        automatically creates 
                        <STRONG>SAParam</STRONG> object to 
                        represent the function return value. This option allows to cancel 
                        creating this 
                        <STRONG>SAParam</STRONG>  
                        object.</P>
                        <P><EM>Valid values</EM>: &quot;Ignore&quot; (SQLAPI++ does not create 
                        <STRONG>SAParam</STRONG> 
                        object to represent 
                        function return value), &quot;Default&quot; (SQLAPI++