Mysql database and table building: the difference between utf8 and utf8mb4

1） brief introduction

   MySQL stay 5.5.3 Then I added this utf8mb4 The coding ,mb4 Namely most bytes 4 It means , Designed to be compatible with four bytes unicode. Fortunately utf8mb4 yes utf8 Superset , In addition to changing the code to utf8mb4 There is no need to make any other conversion . Of course , To save space , In general use utf8 That's enough. .

2） Content description

    It said that since utf8 Can save most Chinese characters , Then why use utf8mb4 Well ? original mysql Supported by utf8 The maximum character length of the encoding is 3 byte , If you encounter 4 Byte wide characters will be inserted into the exception . Three bytes UTF-8 The best way to code Unicode Character is a 0xffff, That is to say Unicode The Basic Multilingual plane in (BMP). in other words , Anything that is not in the basic multi text plane Unicode character , Can't use Mysql Of utf8 Character set storage . Include Emoji expression (Emoji It's a special kind Unicode code , Common in ios and android On the cell phone ), And a lot of unusual Chinese characters , And any new Unicode Characters and so on (utf8 The shortcomings of ).