postgresql.html

能够连接各种数据库的API

                <P>  The SQLAPI++ Library requires libpq 
            version 7.1.x or higher.</P>
            <P>For more details see <A 
            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>
                    PostgreSQL</STRONG> server in the following way:</P>
                    <P>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
                        <STRONG 
            >SA_ReadUncommitted</STRONG> =  
            'READ COMMITTED'<BR><STRONG > 
                        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; SA_ReadCommitted</STRONG> = 
             'READ COMMITTED' <BR 
                        ><STRONG 
            >&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
            SA_RepeatableRead</STRONG> = 
  
   'READ COMMITTED'<BR>
                        <STRONG>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; SA_Serializable</STRONG> = 
             '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>The table below shows how SQLAPI++ data 
            types correspond with servers original data types:</P>
            <P><EM>SA_dtLongBinary</EM> 
            &lt;=  &gt; BYTEA<BR><EM>SA_dtLongChar</EM> &lt;=  &gt; TEXT<BR 
            ><EM>SA_dtBLob</EM> &lt; =         &gt;  Large 
            Object<BR><EM>SA_dtCLob &lt; 
            </EM>=&gt; Large Object</EM></P>
            <P>
            Working with PostgreSQL Large Objects data 
            (Oid field type) in <STRONG>PostgreSQL</STRONG> server has some 
            particular features. Generally when you fetch Oid field data (which 
            can point to any object, not necessary PostgreSQL Large Object) 
            SQLAPI++ returns its value as a number (SQLAPI++ returns an object 
            identifier). If you want to retrieve Oid field as PostgreSQL Large 
            Object you should set command-related option 
            <STRONG>OidTypeInterpretation</STRONG> to 
            <EM>&quot;LargeObject&quot;</EM>value before the command execution. 
            See <A 
            href="../OnLineDoc/Command_setOption.html">SACommand::setOption</A> 
            for more detailes.</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><STRONG> PostgreSQL</STRONG> server does not support 
               returning output parameters from stored procedures.</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>PQrequestCancel</STRONG>  function to cancel a query. To get more 
            details see <STRONG>  <STRONG>PQrequestCancel</STRONG></STRONG> function 
            description in <STRONG>PostgreSQL</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>PostgreSQL</STRONG> server:</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>UseDLLonWin32</STRONG> 
                        </P></STRONG>
                        <P align=center>
                        Connection related. 
                        Should be specified before the first connection is made.<STRONG></STRONG> 
                        </P> 
                        </TD>
                    <TD>
                        <P>     
                          Forces     
                          SQLAPI++ Library to use pq.dll 
                        or     
                          libpq.dll when you are working on Win32 platform.<BR >       
                          
	                <BR><EM>Valid values</EM>
                     : 
                        &quot;CygWin&quot; and &quot;Native&quot;.
                    <BR><EM>Default 
                        value</EM>: &quot;Native&quot;. SQLAPI++ 
                        uses libpq.dll as the   
                           default 
                        API DLL.<BR>   
                              
                                Setting   
                              
                                &quot;CygWin&quot; 
                        value of this option forces SQLAPI++   
                           to use pq.dll.</P></TD></TR>
                <TR>
                    <TD><STRONG>
                        <P align=center>
                        <STRONG>OidTypeInterpretation</STRONG> 
                        </P>