晋太元中,武陵人捕鱼为业。缘溪行,忘路之远近。忽逢桃花林,夹岸数百步,中无杂树,芳草鲜美,落英缤纷。渔人甚异之,复前行,欲穷其林。 林尽水源,便得一山,山有小口,仿佛若有光。便舍船,从口入。初极狭,才通人。复行数十步,豁然开朗。土地平旷,屋舍俨然,有良田、美池、桑竹之属。阡陌交通,鸡犬相闻。其中往来种作,男女衣着,悉如外人。黄发垂髫,并怡然自乐。 见渔人,乃大惊,问所从来。具答之。便要还家,设酒杀鸡作食。村中闻有此人,咸来问讯。自云先世避秦时乱,率妻子邑人来此绝境,不复出焉,遂与外人间隔。问今是何世,乃不知有汉,无论魏晋。此人一一为具言所闻,皆叹惋。余人各复延至其家,皆出酒食。停数日,辞去。此中人语云:“不足为外人道也。”(间隔 一作:隔绝) 既出,得其船,便扶向路,处处志之。及郡下,诣太守,说如此。太守即遣人随其往,寻向所志,遂迷,不复得路。 南阳刘子骥,高尚士也,闻之,欣然规往。未果,寻病终。后遂无问津者。
|
Server : Apache System : Linux srv.rainic.com 4.18.0-553.47.1.el8_10.x86_64 #1 SMP Wed Apr 2 05:45:37 EDT 2025 x86_64 User : rainic ( 1014) PHP Version : 7.4.33 Disable Function : exec,passthru,shell_exec,system Directory : /usr/share/doc/unixODBC/doc/ProgrammerManual/Tutorial/ |
Upload File : |
<HTML>
<HEAD>
<META HTTP-EQUIV="Content-Type" content="text/html; charset=iso-8859-1">
<TITLE>Fetching Data</TITLE>
<LINK REL="StyleSheet" Href="odbc.css">
</HEAD>
<BODY bgcolor="white">
<table width="90%" cols="3" border="0">
<TR>
<TD colspan="3" class="big">Fetching data from a result set</TD>
</TR>
<TR>
<TD colspan="3"><P>If the execution of the statement went fine you are now able to fetch
the data <A Href="gloss.html#col">column</A> by column. May be you would first like to know
how many columns there are in the result set (if you use a <CODE> SELECT * FROM tkeyuser</CODE>
you wouldn't know in your program). A call to <a href="gloss.html#ccol"><CODE>SQLNumResultCols</CODE></A>.
This function takes the statement handle and a pointer to an integer variable which will yield the
number of columns after the call.</P>
Knowing that much we can add this to our program:
<CODE><PRE>
<FONT COLOR="green">// At the beginning add:</FONT>
SQLSMALLINT V_OD_colanz; <FONT COLOR="green">// Num of columns</FONT>
<FONT COLOR="green">// At the end add:</FONT>
V_OD_erg=SQLNumResultCols(V_OD_hstmt,&V_OD_colanz);
if ((V_OD_erg != SQL_SUCCESS) &&
(V_OD_erg != SQL_SUCCESS_WITH_INFO))
{
printf("Fehler im ResultCols %d\n",V_OD_erg);
SQLFreeHandle(SQL_HANDLE_STMT,V_OD_hstmt);
SQLFreeHandle(SQL_HANDLE_DBC,V_OD_hdbc);
SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);
exit(0);
}
printf("Number of Columns %d\n",V_OD_colanz);
</PRE></CODE>
<P>
The next thing you need to know is how many <A href="gloss.html#row">rows</A> have
been returned by the query. A call to <A HREF="gloss.html#crow"><CODE>SQLRowCount</CODE></A> should
quench your thirst for knowledge.
</P>
<P>
The last thing to do is to fetch the data itself from the result set. You should call <A HREF="gloss.html#fetc"><CODE>SQLFetch</CODE></A>
with a statement handle (which has been allocated and <CODE>SQLBind</CODE> has been called for all columns).
<CODE>SQLFetch</CODE> returns <CODE>SQL_NO_DATA</CODE> if there is no more data in the result set.
</P>
<P>So here is the complete source code. Real C-programmers will moan in disgust
how inefficient the program is coded, but I prefer it that way (doesn't it look a little bit like PASCAL?).
Take it as a starting point for your own endeavors with ODBC.</P>
<CODE class="list"><PRE>
/* odbc.c
testing unixODBC
*/
#include <stdlib.h>
#include <stdio.h>
#include <odbc/sql.h>
#include <odbc/sqlext.h>
#include <odbc/sqltypes.h>
SQLHENV V_OD_Env; <FONT COLOR="green">// Handle ODBC environment</FONT>
long V_OD_erg; <FONT COLOR="green">// result of functions</FONT>
SQLHDBC V_OD_hdbc; <FONT COLOR="green">// Handle connection</FONT>
char V_OD_stat[10]; <FONT COLOR="green">// Status SQL</FONT>
SQLINTEGER V_OD_err,V_OD_rowanz,V_OD_id;
SQLSMALLINT V_OD_mlen,V_OD_colanz;
char V_OD_msg[200],V_OD_buffer[200];
int main(int argc,char *argv[])
{
<FONT COLOR="green">// 1. allocate Environment handle and register version </FONT>
V_OD_erg=SQLAllocHandle(SQL_HANDLE_ENV,SQL_NULL_HANDLE,&V_OD_Env);
if ((V_OD_erg != SQL_SUCCESS) && (V_OD_erg != SQL_SUCCESS_WITH_INFO))
{
printf("Error AllocHandle\n");
exit(0);
}
V_OD_erg=SQLSetEnvAttr(V_OD_Env, SQL_ATTR_ODBC_VERSION, (void*)SQL_OV_ODBC3, 0);
if ((V_OD_erg != SQL_SUCCESS) && (V_OD_erg != SQL_SUCCESS_WITH_INFO))
{
printf("Error SetEnv\n");
SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);
exit(0);
}
<FONT COLOR="green">// 2. allocate connection handle, set timeout</FONT>
V_OD_erg = SQLAllocHandle(SQL_HANDLE_DBC, V_OD_Env, &V_OD_hdbc);
if ((V_OD_erg != SQL_SUCCESS) && (V_OD_erg != SQL_SUCCESS_WITH_INFO))
{
printf("Error AllocHDB %d\n",V_OD_erg);
SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);
exit(0);
}
SQLSetConnectAttr(V_OD_hdbc, SQL_LOGIN_TIMEOUT, (SQLPOINTER *)5, 0);
<FONT COLOR="green">// 3. Connect to the datasource "web" </FONT>
V_OD_erg = SQLConnect(V_OD_hdbc, (SQLCHAR*) "web", SQL_NTS,
(SQLCHAR*) "christa", SQL_NTS,
(SQLCHAR*) "", SQL_NTS);
if ((V_OD_erg != SQL_SUCCESS) && (V_OD_erg != SQL_SUCCESS_WITH_INFO))
{
printf("Error SQLConnect %d\n",V_OD_erg);
SQLGetDiagRec(SQL_HANDLE_DBC, V_OD_hdbc,1,
V_OD_stat, &V_OD_err,V_OD_msg,100,&V_OD_mlen);
printf("%s (%d)\n",V_OD_msg,V_OD_err);
SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);
exit(0);
}
printf("Connected !\n");
V_OD_erg=SQLAllocHandle(SQL_HANDLE_STMT, V_OD_hdbc, &V_OD_hstmt);
if ((V_OD_erg != SQL_SUCCESS) && (V_OD_erg != SQL_SUCCESS_WITH_INFO))
{
printf("Fehler im AllocStatement %d\n",V_OD_erg);
SQLGetDiagRec(SQL_HANDLE_DBC, V_OD_hdbc,1, V_OD_stat,&V_OD_err,V_OD_msg,100,&V_OD_mlen);
printf("%s (%d)\n",V_OD_msg,V_OD_err);
SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);
exit(0);
}
SQLBindCol(V_OD_hstmt,1,SQL_C_CHAR, &V_OD_buffer,150,&V_OD_err);
SQLBindCol(V_OD_hstmt,2,SQL_C_ULONG,&V_OD_id,150,&V_OD_err);
V_OD_erg=SQLExecDirect(V_OD_hstmt,"SELECT dtname,iduser FROM tkeyuser order by iduser",SQL_NTS);
if ((V_OD_erg != SQL_SUCCESS) && (V_OD_erg != SQL_SUCCESS_WITH_INFO))
{
printf("Error in Select %d\n",V_OD_erg);
SQLGetDiagRec(SQL_HANDLE_DBC, V_OD_hdbc,1, V_OD_stat,&V_OD_err,V_OD_msg,100,&V_OD_mlen);
printf("%s (%d)\n",V_OD_msg,V_OD_err);
SQLFreeHandle(SQL_HANDLE_STMT,V_OD_hstmt);
SQLFreeHandle(SQL_HANDLE_DBC,V_OD_hdbc);
SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);
exit(0);
}
V_OD_erg=SQLNumResultCols(V_OD_hstmt,&V_OD_colanz);
if ((V_OD_erg != SQL_SUCCESS) && (V_OD_erg != SQL_SUCCESS_WITH_INFO))
{
SQLFreeHandle(SQL_HANDLE_STMT,V_OD_hstmt);
SQLDisconnect(V_OD_hdbc);
SQLFreeHandle(SQL_HANDLE_DBC,V_OD_hdbc);
SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);
exit(0);
}
printf("Number of Columns %d\n",V_OD_colanz);
V_OD_erg=SQLRowCount(V_OD_hstmt,&V_OD_rowanz);
if ((V_OD_erg != SQL_SUCCESS) && (V_OD_erg != SQL_SUCCESS_WITH_INFO))
{
printf("Number ofRowCount %d\n",V_OD_erg);
SQLFreeHandle(SQL_HANDLE_STMT,V_OD_hstmt);
SQLDisconnect(V_OD_hdbc);
SQLFreeHandle(SQL_HANDLE_DBC,V_OD_hdbc);
SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);
exit(0);
}
printf("Number of Rows %d\n",V_OD_rowanz);
V_OD_erg=SQLFetch(V_OD_hstmt);
while(V_OD_erg != SQL_NO_DATA)
{
printf("Result: %d %s\n",V_OD_id,V_OD_buffer);
V_OD_erg=SQLFetch(V_OD_hstmt);
} ;
SQLFreeHandle(SQL_HANDLE_STMT,V_OD_hstmt);
SQLDisconnect(V_OD_hdbc);
SQLFreeHandle(SQL_HANDLE_DBC,V_OD_hdbc);
SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);
return(0);
}
</PRE>
</CODE>
If I find some more time I will add something about diagnostics, cursor positioning updating and and and...
</TD>
</TR>
</TABLE>
</BODY>
</HTML>