MySQL 연산자 중에 ~ 연산자가 있다.
이 연산자는 bit 열의 1의보수를 구하는 말그대로 비트를 거꾸로 뒤집는 연산자(invert)이다.
이 연산자를 사용하면 결과값으로 unsigned 64-bit integer. 즉 BIGINT UNSIGNED 값이 나온다.
그럼 0을 1의 보수로 구하면 어떻게 될까? 바로 BIGINT UNSIGNED의 최대값이 나오게된다.
이값을 shift 연산이나 Bit and 연산을 하면 쉽게 구할수 있다.
mysql> select ~0;
+----------------------+
| ~0 |
+----------------------+
| 18446744073709551615 |
+----------------------+
1 row in set (0.00 sec)
mysql> SELECT ~0 as bigint_unsigned
-> , ~0 >> 32 as int_unsigned
-> , ~0 >> 40 as mediumint_unsigned
-> , ~0 >> 48 as smallint_unsigned
-> , ~0 >> 56 as tinyint_unsigned
-> , ~0 >> 1 as bigint_signed
-> , ~0 >> 33 as int_signed
-> , ~0 >> 41 as mediumint_signed
-> , ~0 >> 49 as smallint_signed
-> , ~0 >> 57 as tinyint_signed
-> \G
*************************** 1. row ***************************
bigint_unsigned: 18446744073709551615
int_unsigned: 4294967295
mediumint_unsigned: 16777215
smallint_unsigned: 65535
tinyint_unsigned: 255
bigint_signed: 9223372036854775807
int_signed: 2147483647
mediumint_signed: 8388607
smallint_signed: 32767
tinyint_signed: 127
1 row in set (0.00 sec)
mysql> SELECT ~0 as bigint_unsigned
-> , ~0 & 0xFFFFFFFF as int_unsigned
-> , ~0 & 0xFFFFFF as mediumint_unsigned
-> , ~0 & 0xFFFF as smallint_unsigned
-> , ~0 & 0xFF as tinyint_unsigned
-> , ~0 & 0x7FFFFFFFFFFFFFFF as bigint_signed
-> , ~0 & 0x7FFFFFFF as int_signed
-> , ~0 & 0x7FFFFF as mediumint_signed
-> , ~0 & 0x7FFF as smallint_signed
-> , ~0 & 0x7F as tinyint_signed
-> \G
*************************** 1. row ***************************
bigint_unsigned: 18446744073709551615
int_unsigned: 4294967295
mediumint_unsigned: 16777215
smallint_unsigned: 65535
tinyint_unsigned: 255
bigint_signed: 9223372036854775807
int_signed: 2147483647
mediumint_signed: 8388607
smallint_signed: 32767
tinyint_signed: 127
1 row in set (0.00 sec)
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