For example:



Select * from T where col like ??%abcd??;



The table T is myisam table and we created a index on col.



As we known, this like sql does not use the index created on col, it confuse
me, why?



I think in mysiam engine, the index data is smaller, it can use index link
list to optimize it so as to reduce the disk scan than to the whole table
scan.



Thanks.



Zhigang