1, the priority field type
整型>data,time>char,varchar>blob
Integer, time fast operation, space-saving
char, varchar to consider the conversion and sorting proof sets character set, slow
Blob can not use temporary tables memory
2, do not use too much memory
Large field waste of memory, affect the speed
Such as: varchar (10), the same varchar (300) storing content, but joint investigation Table, varchar (300) to use more memory
3, try to avoid using null
null is not conducive to the index, use a special byte to mark
Take up more memory on disk
4, Enum Column Description
1, enum is an integer column inside to store
2, enum enum columns and columns of the fastest-related
3, enum associated with char, need to be transformed, to spend more time
4, when the very long char, enum is still a fixed-length integer, the greater the amount of data when queried, the more obvious advantages enum
5, enum associated with char / varchar, due to the conversion speed than enum - enum, char - char slower
But in particularly large amount of data, you can save IO