   Attention: the data frames do not match exactly, but as no primary key columns are
   provided, the row and column matches cannot be computed.

 Schemas
 ▔▔▔▔▔▔▔
   ┏━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━┓
   ┃   Left only   ┃         In common         ┃  Right only   ┃
   ┃   2 columns   ┃         3 columns         ┃   1 column    ┃
   ┡━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━┩
   │ col_a [Int64] │  col_x [Int16 -> UInt16]  │ col_d [Int64] │
   ├───────────────┼───────────────────────────┼───────────────┤
   │ col_b [Int32] │  col_y [Int8 -> Float32]  │               │
   ├───────────────┼───────────────────────────┼───────────────┤
   │               │ (+1 column with matching  │               │
   │               │        data type)         │               │
   └───────────────┴───────────────────────────┴───────────────┘
