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我想在C中使用ECPG - 嵌入式SQL - 使用游标从表格中获取一行。postgresql在不知道表格详细信息的情况下获取一行
例如:
struct{
char *col1;
char *col2;
....
}test_struct;
EXEC SQL DECLARE mycursor CURSOR FOR select * from test
EXEC SQL SET TRANSCATION read only
EXEC SQL OPEN mycursor
EXEC SQL FETCH FROM mycursor INTO :test_struct
但似乎我必须定义对应表测试一个结构test_struct,这意味着我已经知道如何在表中的列以及其类型和名称。如何从任何我不知道其模式的表中获取一行?
例如:
select * from arbitrary_table_in_my_db
//////////////////////////////////// /////////////////////
///修改: SQLDA正常工作,这里是从http://www.postgresql.org/message-id/[email protected]
示例代码//取得了一些修改
#include <pgtypes_date.h>
#include <pgtypes_numeric.h>
EXEC SQL include sqlda.h;
sqlda_t *sqlda1;
int
main(void)
{
EXEC SQL CONNECT TO ....
EXEC SQL DECLARE cur CURSOR FOR SELECT * FROM test;
EXEC SQL OPEN cur;
EXEC SQL WHENEVER NOT FOUND DO BREAK;
while (1) {
/* Open a cursor and assign descriptor to the cursor */
EXEC SQL FETCH NEXT FROM cur INTO DESCRIPTOR sqlda1;
while (1) {
int i;
char name_buf[1024];
char var_buf[1024];
for (i=0 ; i<sqlda1->sqld ; i++) {
sqlvar_t v = sqlda1->sqlvar[i];
char *sqldata = v.sqldata;
short sqllen = v.sqllen;
strncpy(name_buf, v.sqlname.data, v.sqlname.length);
name_buf[v.sqlname.length] = '\0';
strncpy(var_buf, sqldata, sqllen);
var_buf[sqllen] = '\0';
if(v.sqltype == 16)
printf("%s = %s, (type:%d)\n", name_buf, PGTYPESnumeric_to_asc((numeric*)sqldata,0), v.sqltype);
else if(v.sqltype == 18){
printf("%s = %s, (type:%d)\n", name_buf, PGTYPESdate_to_asc(*v.sqldata), v.sqltype);
}
else
printf("%s = %s, (type:%d)\n", name_buf, var_buf, v.sqltype);
}
printf("\n");
if (sqlda1->desc_next==NULL)
break;
}
}
EXEC SQL CLOSE cur;
EXEC SQL COMMIT;
EXEC SQL DISCONNECT ALL;
return (0);
}
这可能是有趣的;它讨论了如何读取任意的'RECORD'结果。 http://www.postgresql.org/message-id/[email protected] – 2013-02-27 00:12:08
谢谢克雷格。但它仍然定义了一个特定的结构来存储提取结果,我的问题是:是否有可能获取一行到泛型结构? – camino 2013-02-27 00:33:48
@caminio我不使用ECPG,但通常在Pg中,您希望将该行转换为'xml','json'或'hstore'服务器端,并将其作为单个字段返回。 – 2013-02-27 01:23:30