When an index is created, there is one column I have doubts about, in concern with the physical linking of the data nodes.
When 2 "seq_in_index" are same, how are they placed in the node? How is the structure of the index binary tree in that case?
It is the position of the column in the index.
INDEX some_idx(column_a, column_b)
1 and for
In your case the compound index is
INDEX email(email, status)