What is the difference between inner join and join?

I have two tables, A and B. They are almost identical but in different sorted by rows.

I would like to tie them up by rows. Should I use innerjoin or join?

What is the difference between inner join and join? Thanks for any help.

Answer 1

[Jan]

For a join both tables requires the same variables. For an innerjoin the overlapping variables are chosen.

A look into the documentation is useful:

help join
help innerjoin

You can create an innerjoin of:

a = table({'a' 'b' 'c' 'e' 'h'}', [1 2 3 11 17]', 'VariableNames',{'Key1' 'Var1'})
b = table({'a' 'b' 'd' 'e'}', [4 5 6 7]', 'VariableNames',{'Key1' 'Var2'})

The result contains the overlapping keys 'a', 'b', 'e' only. You cannot join them due to the not matching 'c' and 'h'. But you can join:

a = table({'a' 'b' 'c' 'e' 'h'}', [1 2 3 11 17]', 'VariableNames', {'Key1' 'Var1'})
b = table({'a' 'b' 'h' 'e' 'c'}', [4 5 6 7  8]',  'VariableNames', {'Key1' 'Var2'})

Here the join and innerjoin give the same results, so it does not matter, which one you run.

Note:

• join: both tables need the same keys
• innerjoin: The result contains the overlapping keys only
• outerjoin: The result contains all keys of both tables and fills missing values with dummies.

[JFz]

Thank you!