sqlite3 打印的三种方式

当使用SELECT语句等的时候，想要打印信息，这里提供三种方式

1. 使用sqlite_exec的回调函数。

sqlite3_exec(sqlite3*, const char *sql, sqlite_callback, void *data, char **errmsg)

第四个参数data是callback的第一个参数。

int displaycb(void *para,int ncolumn,char ** columnvalue,char *columnname[])
{
 
	for(int i = 0; i < ncolumn; i++)
	{
		printf("key:%s----> value:%s\n",columnname[i],columnvalue[i]);
	}
 
	return 0;
}

2. 使用sqlite3_get_table去获取信息，将二维数组内容打印

int sql_search_info(char* sql) {
	int len;
	int i = 0;
	int nrow = 0;
	int ncolumn = 0;
	char* zErrMsg = NULL;
	char** azResult = NULL; //二维数组存放结果

	sqlite3_get_table(g_db, sql, &azResult, &nrow, &ncolumn, &zErrMsg);
	if (nrow == 0) {
		printf("cannot find data\n");
		return -1;
	}

	char label[512] = { 0 };
	for (int i = 0; i <= 16 * ncolumn; i++)
		sprintf(label + strlen(label), "-");
	
	printf("%s\n", label);
	for (i = 0; i < (nrow + 1) * ncolumn; i++)
	{
		printf("|%-8s\t", azResult[i]);

		if ((i + 1) % ncolumn == 0) {
			printf("|\n");
			printf("%s\n", label);
		}

	}
	return 0;
};

3. 使用sqlite3_prepare_v2 => sqlite3_column_count => sqlite3_step => sqlite3_finalize 等一系列函数

int sql_search_lol_info() {
	champion cham;
	memset(&cham, 0, sizeof(champion));
	int ID = 0;
	char uptime[32] = { 0 };
	char formtime[32] = { 0 };

	char* sql = sqlite3_mprintf("select * from LOL");

	sqlite3_stmt* stmt = NULL;
	int ncolumn = 0;
	const char* column_name;
	int vtype, i;
	int rc;

	rc = sql_prepare(sql, &stmt);  //调用函数在下面

	if (0 == rc) {
		ncolumn = sqlite3_column_count(stmt);
		while (sqlite3_step(stmt) == SQLITE_ROW) {
			for (i = 0; i < ncolumn; i++) {
				vtype = sqlite3_column_type(stmt, i);
				column_name = sqlite3_column_name(stmt, i);

				switch (vtype) {
				case SQLITE_INTEGER:
					if (!strcmp("id", column_name))
						ID = sqlite3_column_int(stmt, i);	
					if (!strcmp("age", column_name))
						cham.age = sqlite3_column_int(stmt, i);
					break;
				case SQLITE_FLOAT:
					if (!strcmp("difficulty", column_name))
						cham.diff = (float)sqlite3_column_double(stmt, i);
					break;
				case SQLITE_TEXT:
					if (!strcmp("name", column_name)) 
						strcpy(cham.name, (const char*)sqlite3_column_text(stmt, i));					
					if (!strcmp("organization", column_name)) 
						strcpy(cham.org, (const char*)sqlite3_column_text(stmt, i));
					if (!strcmp("role", column_name)) 
						strcpy(cham.role, (const char*)sqlite3_column_text(stmt, i));
					if (!strcmp("weapon", column_name)) 
						strcpy(cham.weapon, (const char*)sqlite3_column_text(stmt, i));
					}
					break;
				case SQLITE_BLOB:
					break;
				case SQLITE_NULL:
					break;
				default:
					break;
				}
			}
			printf("%-4d %-8s %-4d %-8s %-8s %-16s %-4f\n", ID, cham.name, cham.age, cham.org, cham.role, cham.weapon, cham.diff);
		}
	}
    sqlite3_finalize(stmt);
	return 0;
}

int sql_prepare(const char* sql, sqlite3_stmt** stmt) {
	if (NULL == sql || NULL == stmt) {
		printf("param error");
		return -1;
	}

	if (NULL == g_db) {
		printf("_g_db error");
		return -1;
	}

	if (SQLITE_OK != sqlite3_prepare_v2(g_db, sql, -1, stmt, 0)) {
		printf("sqlite3_prepare_v2 error");
		return -1;
	}

	return 0;
}

对比：

使用get_table有时候会出问题，虽然我没有遇到过，但是当默写特殊情况发生，会导致错误。附上一个我找到的原因。

https://blog.csdn.net/chenliang0224/article/details/90046522?depth_1-utm_source=distribute.pc_relevant.none-task&utm_source=distribute.pc_relevant.none-task

至于使用回调函数和第三种，虽然第三种麻烦了点，不过这也是官方推荐的方式。而且更方便控制。所以我推荐使用第三种方式。