MySQL Numeric Types(数字类型)

Integer

Type	Storage (Bytes)	Minimum Value Signed	Minimum Value Unsigned	Maximum Value Signed	Maximum Value Unsigned
TINYINT	1	-128	0	127	255
SMALLINT	2	-32768	0	32767	65535
MEDIUMINT	3	-8388608	0	8388607	16777215
INT	4	-2147483648	0	2147483647	4294967295
BIGINT	8	-263	0	2^63-1	2^64-1

Decimal

salary DECIMAL(5,2)

Float&Double

FLOAT(7,4) will look like -999.9999 when displayed.
MySQL performs rounding when storing values, so if you insert 999.00009 into a FLOAT(7,4) column, the approximate result is 999.0001.

Bit

If you assign a value to a BIT(M) column that is less than M bits long, the value is padded on the left with zeros. For example, assigning a value of b’101’ to a BIT(6) column is, in effect, the same as assigning b’000101’.

参考:
https://dev.mysql.com/doc/refman/8.0/en/numeric-types.html