在ORMLite中按外国实体的属性排序

Question

如何在ORMLite中构建一个查询,以便我可以使用orderBy函数(使用带有原始字符串或参数化函数的函数)引用与我正在构建查询的dao不同的实体的属性. ？我的查询是这样构建的:

// Inner query for performances
QueryBuilder<Performance, String> performancesQB = performanceDao.queryBuilder();
performancesQB.selectColumns("performance_id");
SelectArg performanceSelectArg = new SelectArg();
performancesQB.where().lt("date", performanceSelectArg);

// Outer query for Order objects, where the id matches in the performance_id
// from the inner query
QueryBuilder<Order, String> ordersQB = orderDao.queryBuilder();
ordersQB.where().isNull("user_id").and().in("performance_id", performancesQB);
ordersQB.orderByRaw("performances.date DESC");
pastOrdersQuery = ordersQB.prepare();

每当我尝试执行此查询时,我得到的异常是:

android.database.sqlite.SQLiteException: no such column: performances.date:,
   while compiling: SELECT * FROM `orders` WHERE
     (`user_id` IS NULL AND `performance_id` IN
     (SELECT `performance_id` FROM `performances` WHERE `date` < ? ) )
     ORDER BY performances.date DESC 

我在这里看到的唯一解决方案是使用JOIN而不是嵌套选择自己编写原始查询.愿这是一个很好的解决方案吗？

Answer 1

ORMLite现在支持简单的JOIN查询.这里有关于这个主题的文档:

http://ormlite.com/docs/join-queries

所以你的查询现在看起来像:

QueryBuilder<Performance, String> performancesQB = performanceDao.queryBuilder();
SelectArg performanceSelectArg = new SelectArg();
performancesQB.where().lt("date", performanceSelectArg);
performancesQB.orderBy("date", false);

// query for Order objects, where the id matches
QueryBuilder<Order, String> ordersQB = orderDao.queryBuilder();
ordersQB.join(performancesQB).where().isNull("user_id");
pastOrdersQuery = ordersQB.prepare();