MySQL digital type learning notes

Numeric type

Recently in to see 《MySQL Technology insider ：SQL Programming 》 And made notes , So this blog is a blog of note type , Share it for your review , Can also help others

• integer

type	Occupancy space	minimum value (SIGNED)	Maximum (SIGNED)	minimum value (UNSIGNED)	Maximum (UNSIGNED)
TINYINT	1	-128	127	0	255
SMALLINT	2	-32768	32767	0	65535
MEDIUMINT	3	-8388608	8388607	0	16777215
INT	4	-2147483648	2147483647	0	4294967295
BIGINT	8	-9223372036854775808	9223372036854775808	0	18446744073709551615

• A type of
  A type of , Keywords are bit, The bit type is used to store the value of the bit field ,BIT(M),M Indicates the value of the number of bits allowed to be stored ,M For the range of 1 To 64, The space occupied is (M+7)/8 byte

Be careful ： If the length of the assigned value is less than M position , Use it on the left of the value 0 fill

Log in and copy

      
      

       
       #  Create a table 
       
       
CREATE TABLE t(a BIT(4));
       
       
#  Write data 
       
       
INSERT INTO t SELECT b'1000';
       
       
#  Inquire about , Display the string in the new version , You can't check it directly 
       
       
SELECT * FROM t;
       
       
#  Bit type , It can be used HEX function , The result is a number 8(16 Base number )
       
       
SELECT HEX(a) FROM t;
      
      
      
      

       
       
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• floating-point （ Imprecise type ）
  MySQL Two floating point types are supported ： Single precision FLOAT Type and double precision DOUBLE type
• High precision type
  DECIMAL and NUMERIC yes MySQL Types with relatively high progress , Grammar is DECIMAL(M,N)、NUMERIC(M,N),M Representation precision , That is, the number of digits of the whole value ,, Two types of maximum digits M All for 65,N Indicates the scale , That is, the number of digits after the decimal point of the whole value