DB-Library for c 如何使用嵌套sql

我想在遍历记录的同时,改变相关表的记录,下面是部份代码,语法上通过了.前面的sql 也查出了数据,
但是内层执行update时报错.像这种多层的,怎么调用,谢谢

sprintf(sql,"select top 100 * from test);
dbcmd(dbproc,sql);
ret=dbsqlexec(dbproc);
if(ret==FAIL){

return
}
ret = dbresults(dbproc);
if(ret == SUCCEED){

dbbind(dbproc, 1, STRINGBIND, (DBINT)0, (unsigned char*) lsh);
dbbind(dbproc, 3, STRINGBIND, (DBINT)0, (unsigned char*)content);

while (dbnextrow(dbproc) != NO_MORE_ROWS)
{

sprintf(sql,"update test set content='123' where lsh ='%s'",lsh);
dbcmd(dbproc,sql);
ret=dbsqlexec(dbproc); //这里报错,,像这种嵌套sql 语句要怎么用
if(ret==FAIL){
return;
}
dbfreebuf(dbproc);
}