Power Query和Power Map是微软前不久在WPC上发布的Power BI中新的针对Excel的功能.借助这两样功能,自助式BI将更方便你发现和处理数据并且丰富数据的可视化功能. Power Query和Power Map的前身分别是Data Explorer和GeoFlow,这两样功能在SQL Server 2014 CTP1里都有提到.结合Power Pivot和Power View,这四大功能组成了微软最新的Power BI系列. 本文源自微软商业智能官方博客里的内容,主要演示
Different query operators in MongoDB treat null values differently. The examples on this page use the db.collection.find() method in the mongo shell. To populate the users collection referenced in the examples, run the following in mongo shell: db.us