db collection count example

Http://www.mongodb.org/display/docs/advanced?queries=advancedqueries-conditionaloperators:,>= MongoDB update data syntaxIn the previous article "MongoDB query syntax", I introduced the common query syntax of MongoDB, and the update operation of

Original: LINQ to SQL (Group by/having/count/sum/min/max/avg operator)Group by/having operatorScenario : grouping data to narrow the scope for us to find data.Description : An enumerable object that is assigned and returned after a group operation

This article transferred from: http://www.cnblogs.com/jack-liang/archive/2011/03/22/1991554.htmlGroup by/having operatorScenario : grouping data to narrow the scope for us to find data.Description : An enumerable object that is assigned and returned

Group by/having operatorScenario : grouping data to narrow the scope for us to find data.Description : An enumerable object that is assigned and returned after a group operation on an incoming parameter. To group or delay1. Simple form:var q = from

select/distinct operatorApplication Scenario : O (∩_∩) o ... Query for Bai.Description : Unlike the SELECT function in the SQL command, the SELECT and the clauses in the query expression are placed at the end of the expression and the variables in

Http://wenku.baidu.com/link?url= 2rscun4mum1slbh-lhyzptmgfmieukrwaojgkgpkihkheafjcx2y-hvttnmb1bqjpndwaopcflaajfy6k36ioch_d82bk2ccu468uzdrxvgApplication research of data access technology based on linq+to+entityGroup by/having operatorScenario :

1. Simple form:var q = from P in db. ProductsGroup p by P.categoryid into GSelect G;Statement Description: Use GROUP by to divide the product by CategoryID.Description: from P in db. Products means that the product objects are taken out of the table.

The previous article described LINQ, and by the way, the where operation, this begins with the LINQ to SQL statement, which allows you to understand from a statement's perspective that Linq,linq includes LINQ to Objects, LINQ to DataSets, LINQ to

Let's say we have a MongoDB collection,take this simple set as an example, we need to include how many different mobile phone numbers in the collection, the first thought is to use the DISTINCT keyword,db.tokencaller.distinct (' Caller '). LengthIf

Group by/having operatorScenario : grouping data to narrow the scope for us to find data.Description : An enumerable object that is assigned and returned after a group operation on an incoming parameter. To group or delay1. Simple form:GStatement