本文介绍了Google Cloud Datastore中的HAS ANCESTOR和HAS DESCENDANT子句的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我正在研究 Google Cloud Datastore GQL语法-特别是HAS ANCESTOR和HAS DESCENDANT比较运算符.
I'm studying the Google Cloud Datastore GQL grammar - specifically the HAS ANCESTOR and HAS DESCENDANT comparison operators.
提供以下 Person 实体:
- 艾米
- 弗雷德，父母=艾米
- 劳拉，父母=艾米
- Paul
- Agnes ...
下面的GQL查询会产生相同的输出吗?
Would the GQL queries below produce the same output?
SELECT * FROM Person WHERE key_name='Fred' HAS ANCESTOR KEY('Person', 'Amy')
SELECT * FROM Person WHERE KEY('Person', 'Amy') HAS DESCENDANT key_name='Fred'
如果是这样，我不了解HAS DESCENDANT子句的存在.
If so, I don't understand the existence of HAS DESCENDANT clause.
提前谢谢！
推荐答案
这两个GQL查询应产生相同的结果:
These two GQL queries should produce identical results:
SELECT * FROM Person WHERE __key__ HAS ANCESTOR KEY('Person', 'Amy')
SELECT * FROM Person WHERE KEY('Person', 'Amy') HAS DESCENDANT __key__
这篇关于Google Cloud Datastore中的HAS ANCESTOR和HAS DESCENDANT子句的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！