inner-join

Here are how the dataframes columns look like. df1='device number', 'date', ....<<10 other columns>> 3500 records df2='device number', 'date', ....<<9 other columns>> 14,000 records In each data frame, neither 'device number', nor 'date' are unique. However, their combination is unique to identify a row. I am trying to form a new data frame which matches the rows from df1 and df2 where both device number and date are equal, and have all the columns from these df1 and df2. The pandas command I am trying is df3=pd.merge(df1, df2, how='inner', on=['device number', 'date']) However, df3 gives me a

I have a big problem. I try to bind my WPF DataGrid to a table, created with inner join. I have created a class for the info to convert successfully: public class NeshtoSi { public NeshtoSi() { } public string ssn; public string name; public string surname; } And then I create the inner-joined tables. Still when I assign the ItemsSource and all values are transferred properly, but the DataGrid does not visualize them. var dd = from d in dataContext.Medical_Examinations join p in dataContext.Patients on d.SSN equals p.SSN select new NeshtoSi { ssn = d.SSN, name = p.Name, surname = p.Surname };

I'm trying to create a subset of a table (as a materialized view), defined as those records which have a matching record in another materialized view. For example, let's say I have a Users table with user_id and name columns, and a Log table, with entry_id, user_id, activity, and timestamp columns. First I create a materialized view of the Log table, selecting only those rows with timestamp > some_date. Now I want a materliazed view of the Users referenced in my snapshot of the Log table. I can either create it as select * from Users where user_id in (select user_id from Log_mview) or I can do

I’m using JPA 2.1, Hibernate 4.3.6.Final, and MySQL 5.5.37. How do I write a JPQL query that does a join? I’m trying below final String jpqlQuery = "SELECT m FROM Message m LEFT JOIN MessageReadDate mr " + " INNER JOIN m.group g " + " LEFT JOIN g.classroom c " + " LEFT JOIN c.ROSTER u WHERE " + " u.USER = :recipient AND " + " u.ENABLED = 1 AND " + " c.ENABLED = 1 AND " + " g.NAME = '' AND " + " m.author <> :author"; Query query = m_entityManager.createQuery(jpqlQuery); but getting the error “Path expected for join! … Invalid path: 'g.classroom'”. org.hibernate.hql.internal.ast.ErrorCounter -