>error: column is not unique: duplicate value is...
This is when the primary key in the slave (or "B") table is not primary: it has duplicates. In such situation, Anatella doesn't know which row from the slave table to add to the master table since there are many different choices for the same (primary) key. To solve the error, here is a quick fix (i.e. remove the uniqueness check):
A better fix: You can use the box "NaïveDeduplicate" to see the rows that are "in double" and thereafter fix properly the issue with a "rowFilter" box to remove the rows that should not be there.
>...meta-type ... do not match...
Inside Anatella, there are 3 different column types: Key, Float and Unknown/String.
See here for more information on the meta-types inside Anatella.
For the box "append":
* on pin 0: The column named "variable_id" has the meta-type "Float(F)" .
* on pin 1: The column named "variable_id" has the meta-type "Unknown/String(U)".
A column must have the same type on all the input PIN's for the append box to work.
To solve that: just use a changeDataType box (see in attachment).