如何在Iphone应用程序中实现类结构中的主键和外键表数据

Question

如何在sqlite数据库中连接两个表数据

Answer 1

if（sqlite3_open（[dbPath UTF8String]，＆amp; database）== SQLITE_OK）{

    //const char *sql = "select TaskId,TaskName,StartDate,DueDate,Status,CategoryId from ToDo";

    const char *sql = "SELECT TaskId,TaskName,StartDate,DueDate,Status,ToDo.CategoryId,CategoryName FROM ToDo LEFT OUTER JOIN Category ON ToDo.CategoryId=Category.CategoryId";

    sqlite3_stmt *selectstmt;
    if(sqlite3_prepare_v2(database, sql, -1, &selectstmt, NULL) == SQLITE_OK) {

        while(sqlite3_step(selectstmt) == SQLITE_ROW) {

            NSInteger primaryKey = sqlite3_column_int(selectstmt, 0);
            ToDo *toDoObj = [[ToDo alloc] initWithPrimaryKey:primaryKey];
            toDoObj.taskName = [NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt, 1)];
            toDoObj.startDate = [NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt, 2)];
            toDoObj.dueDate = [NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt, 3)];
            toDoObj.status  = sqlite3_column_int(selectstmt, 4);
            toDoObj.categoryId = sqlite3_column_int(selectstmt, 5);
            toDoObj.category = [NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt, 6)];
            toDoObj.isDirty = NO;

            [appDelegate.todoArray addObject:toDoObj];
            [toDoObj release];
        }
    }

}
else
    sqlite3_close(database);