A3 is not included because the two IDs are seperate from each other. If A3 had equaled B1, B2, or B3 then it would have been included in the grouping. However, since B4 is a new ID, it is not included. Another example would be: ID1_A ID2_B Name red apple alpha red strawberry bravo green apple charlie green strawberry bravo green banana delta purple eggplant echo becomes: ID_combined Name_combined red alpha bravo charlie bravo delta purple echo
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