i << n 等于 i * 2^n
i >> n 等于 i / 2^n
i & (2^n-1) 等于 i % 2^n (eg: i&1 <=> i%2, i&3 <=> i%4, i&7 <=> i%8, i&15 <=> i%16)

特性：
	i&0 = 0
	i&i = i
	i|0 = i
	i|i = i
	i^0 = i
	i^i = 0

b字节(n=8b位)有符号整数的值范围是 [ - 2^(n-1), 2^(n-1) -1 ]
b字节(n=8b位)无符号整数的值范围是 [ 0, 2^n - 1 ]

+----------+--------+--------+---------------------+---------------------+
| MySQL    | Go     | C#     | min                 | max                 |
+----------+--------+--------+---------------------+---------------------+
| tinyint  | int8   | sbyte  |                -128 |                 127 |
|  ↳u      | uint8  | byte   |                   0 |                 255 |
| smallint | int16  | short  |              -32768 |               32767 |
|  ↳u      | uint16 | ushort |                   0 |               65535 |
| int      | int32  | int    |         -2147483648 |          2147483647 |
|  ↳u      | uint32 | uint   |                   0 |          4294967295 |
| bigint   | int64  | long   |-9223372036854775808 | 9223372036854775807 |
|  ↳u      | uint64 | ulong  |                   0 |18446744073709551615 |
+----------+--------+--------+---------------------+---------------------+

MySQL还有3字节整数mediumint，(类同int24和uint24)
	min:          -2^23  = -8388608
	max:          2^23-1 =  8388607
	usigned max:  2^24-1 = 16777215

Go的int和uint，C#的nint和nuint，是取决于运行环境的32位或64位有符号整型和无符号整型。

javascript中最大最小安全整数常量
Number.MIN_SAFE_INTEGER          = -9007199254740991
Number.MAX_SAFE_INTEGER = 2^53-1 =  9007199254740991