我正在尝试使用 C 中的 Berkeley Db 开发数据库。我想在数据库中拥有多个数据,然后访问它们。我的代码如下:
#include <sys/types.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <db.h>
#define DATABASE "access.db"
typedef struct {
int id;
char data1[20];
char src[20];
} pearson_record;
int
main()
{
pearson_record s;
char *papa="1.1.1.1";
char *source="papa";
DB *dbp;
DBT key, data;
int ret, t_ret;
if ((ret = db_create(&dbp, NULL, 0)) != 0) {
fprintf(stderr, "db_create: %s\n", db_strerror(ret));
exit (1);
}
if ((ret = dbp->open(dbp, NULL, DATABASE, NULL, DB_BTREE, DB_CREATE, 0664)) != 0) {
dbp->err(dbp, ret, "%s", DATABASE);
goto err;
}
s.id = 10;
strncpy(s.data1, papa, strlen(papa)+1);
strncpy(s.src, source, strlen(source)+1);
memset(&key, 0, sizeof(key));
memset(&data, 0, sizeof(data));
//memset(&s, 0, sizeof(struct pearson_record));
key.data = &(s.id);
key.size = sizeof(int);
data.data = &s;
data.size = sizeof(s);
papa="1.1.1.2";
source="papaa";
strncpy(s.data1, papa, strlen(papa)+1);
strncpy(s.src, source, strlen(source)+1);
if ((ret = dbp->put(dbp, NULL, &key,&data,DB_NOOVERWRITE)) == 0)
printf("db: %d: key stored.\n", *(int *)key.data);
else
{
dbp->err(dbp, ret, "DB->put");
goto err;
}
s.id = 11;
strncpy(s.data1, papa, strlen(papa)+1);
strncpy(s.src, source, strlen(source)+1);
memset(&key, 0, sizeof(key));
memset(&data, 0, sizeof(data));
//memset(&s, 0, sizeof(struct pearson_record));
key.data = &(s.id);
key.size = sizeof(int);
data.data = &s;
data.size = sizeof(s);
papa="1.1.1.2";
source="papaa";
strncpy(s.data1, papa, strlen(papa)+1);
strncpy(s.src, source, strlen(source)+1);
if ((ret = dbp->put(dbp, NULL, &key,&data,DB_NOOVERWRITE)) == 0)
printf("db: %d: key stored.\n", *(int *)key.data);
else
{
dbp->err(dbp, ret, "DB->put");
goto err;
}
pearson_record *ppr;
if ((ret = dbp->get(dbp, NULL, &key, &data, DB_MULTIPLE)) == 0) {
ppr = (pearson_record *) data.data;
printf("db: %d: key retrieved: data was %s,%s. %d\n",
*(int *)key.data, ppr->data1,ppr->src, data.size);
} else {
dbp->err(dbp, ret, "DB->get");
goto err;
}
if ((ret = dbp->get(dbp, NULL, &key, &data, DB_MULTIPLE)) == 0) {
ppr = (pearson_record *) data.data;
printf("db: %d: key retrieved: data was %s,%s. %d\n",
*(int *)key.data, ppr->data1,ppr->src, data.size);
} else {
dbp->err(dbp, ret, "DB->get");
goto err;
}
err:
if ((t_ret = dbp->close(dbp, 0)) != 0 && ret == 0)
ret = t_ret;
exit(ret);
}
现在它说必须设置 DB_DBT_MULTIPLE。我不知道该怎么做。以前没有标志我只得到最后一个条目。任何形式的帮助将不胜感激。提前致谢
最佳答案
如果我没看错你的代码,你就是在用同一个键调用 get
两次,这显然会返回相同的数据。
如果你想遍历记录,你需要使用游标,参见Chapter 4 of Getting Started with Berkeley DB作为一个很好的引用。
关于c - 无法访问 Berkeley DB 使用 C 创建的数据库中的多个数据,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/7237986/