Difference between tinyint and int

problem ：int(1) and tinyint(1) What's the difference ？

A design like this , Anyway, I can't write int(1) Of .

  Look up the ,mysql After the storage type is set in , Storage is fixed length , in other words ,int(1) and int(4) The number of bytes in the hard disk is the same .

We know ,int Type account 4 Bytes ,tinyint Occupy 1 Bytes .int(1) and int(4) The length and storage method are the same , The difference is the length of the display , But set a parameter ： If the column has zerofill Will use 0 Fill display ,int(4) When specified, it will be displayed as 0002.

int(1) and tinyint(4) comparison , sure int Big .

Notice the number in parentheses after the number type , Does not represent length , Indicates the display width , With this varchar、char The following numbers have different meanings .

That is to say, regardless of int What's the number after that , Its storage range is always -2^31 To 2^31 - 1.
 
To sum up, no matter how many numbers are in parentheses for integer data types , The storage space occupied is the same

tinyint A byte   smallint   Two bytes   MEDIUMINT Three bytes  

Obvious ,int(1) and tinyint(1) , When designing a database, you should choose tinyint(1). The less storage space it takes up, the better , Of course, it needs to be enough . Store one like this Single digit field , Or use it tinyint(1) Good. .

summary ：

1. After specifying the type , The storage is fixed in length ,int(1) and int（4） The length and storage method are the same .mysql in ,int（1） and int(4) The difference is the length of the display , But set a parameter ： If the column has zerofill Will use 0 Fill display , Such as 2 int(3) When specified, it will be displayed as 002

2.int Storage 4 Bytes , tinyint   Storage 1 Bytes , The storage length determines the range of numbers they represent .int The range of numbers represented is ： from -2^31 (-2,147,483,648) To 2^31 – 1 (2,147,483,647) The integer data of （ All figures ）.tinyint The range of representation is 0-255 Number between .

3.tinyint(1), and tinyint(3) No difference , save 123 Can be saved , And if the tinyint(3) zerofill Words , Insert value 12, Will store 012,zerofill Auto zero left , That's what limits the display length .

The above summary is a little messy . The following is a brief summary ：

• tinyint(1)   and tinyint(3) No difference , All occupied bytes are one bit , The storage range is the same
• tinyint(3) zerofill , When the inserted data is less than 3 When a , Automatic zero filling on the left , That's what limits the display length
• int(1) and tinyint(1) , When it's enough , Preference tinyint(1), Because it takes less bytes 、 Save a space .
• tinyint A byte   smallint   Two bytes   MEDIUMINT Three bytes  int 4 Bytes  BIGINT 8 Bytes .

however ,varchar(5)   there 5 The limit is the number of stored characters , Characters don't distinguish between high and low （ Regardless of chinese 、 english 、 Numbers ...）.