如何在varbinary列的第N个字节上执行二进制操作？

Question

我已经能够与substring(colname, N, 1)获得的第N个字节出了场，但在这一点上似乎无法治疗的结果为二进制：

> select substring(colname, N, 1) from [...] 
\ 
> select hex(substring(colname, N, 1)) from [...] 
5C 
> select hex(substring(colname, N, 1) & 0xff) from [...] 
0 
> select cast(substring(colname, N, 1) as unsigned integer) from [...] 
0 

相比：

> select cast(0x5c as binary); 
\ 
> select hex(0x5c & 0xff); 
5C 
> select cast(0x5c as unsigned integer); 
92 

---

我想直到结束是这样的：

> select [...] where substring(colname, N, 1) & 0b00100000 = 0b00100000; 

Answer 1

尝试类似的东西：

select ascii(substring(colname,N,1)) from [...]