Cry.. I thought I knew MySQL indexes well

Mysql video tutorial column introduces the real index. You can also see from the figure that the difference between B+ tree and B tree is: All keywords are stored in leaf nodes, non-leaf nodes do not store real data, so leaf nodes can be quickly located. A chain pointer is added to all leaf nodes, which means that all values ​​​​are stored in order, and the distance from each leaf page to the root is the same, which is very suitable for searching range data. ** Therefore, B+Tree can use indexes for <, , >=, BETWEEN, IN, and LIKE that do not start with wildcards. ** Advantages of B+ tree: The number of comparisons is balanced, reducing the number of I/O, improving the search speed, and the search is more stable. The disk read and write cost of B+ tree is lower The query efficiency of B+ tree is more stable    What you need to know is that you Every time you create a table, the system will automatically create an ID-based clustered index (the above B+ tree) for you to store all the data; every time you add an index, the database will create an additional index (the…