If the index is being bypassed, then the RHS of the comparison should be type-cast.
如果会绕过索引,应该对比较表达式的RHS执行类型转换。
2
If you assume that there is an index on COL1 in the above example, if COL1 is type-cast instead of the RHS, then the index will be bypassed and the query will perform a full table scan.