When you are computing a join between several columns, sometime, the primary key is composed of the several columns (instead of, classically, ONE column). This is called a COMPOSITE primary key.
Most Anatella actions only support “normal” primary keys (i.e. primary keys that are defined using one column). Anatella can handle composite primary keys but you need an extra step: you must create one temporary new column that is the concatenation of all the columns inside the COMPOSITE primary key (and use this new, temporary column instead of the columns inside the COMPOSITE primary key).
For example: Let’s assume that we want to compute a join between two tables: table A and table B. The COMPOSITE primary key inside table A is defined using the columns MSISDN and TIME (and the same inside table B). We will have: