问题
Any benchmark, graph anything at all ? Its all academic and theoretical across the web.
Ok its not the first time that this question has been asked, they all say that using CHAR results in faster selects? I even read in MySQL books, its all the same but I have not come across any benchmark that proves this.
Can any one shed some light over this?
回答1:
This is simple logic, to simplify I'll take the example of a CSV file...
would it be faster to search in this line
1231;231;32345;21312;23435552;1231;1;243;211;3525321;44343112;
or this one
12;23;43;54;56;76;54;83;45;91;28;92
as long as you define your length correctly CHAR should be faster as the predefined format help the processing time.
回答2:
The point is, it is not. Not by itself anyway.
What is true however, is that if there are only fixed width fields in the table, MySQL does not need to perform some calculations to find out the beginnings of each field.
Also there might be a difference for very short fields. If you compare CHAR(1) vs VARCHAR(1), the latter takes twice as much memory as the first (in single byte encodings)
回答3:
I guess you should pick up the glove and just do it.
来源：https://stackoverflow.com/questions/3408930/does-anyone-have-considerable-proof-that-char-is-faster-than-varchar