如何按位或为二进制(100)?

问题描述

我有一个binary(100)，我想对它的一个字节与一个常量进行按位或运算.

I have a binary(100), and I want to bitwise OR just one of its bytes with a constant.

知道要怎么做吗?

或者，如何将值存储到binary(100)的字节中?

Alternatively, how can I store a value into a byte of a binary(100)?

推荐答案

首先，考虑BINARY是否实际上是适当的字段类型.与BLOB相比，它具有剥离尾随空格的潜在讨厌"特征. BINARY实际上只是设计为不区分大小写的二进制文本字符串，而不是任意二进制数据的斑点.

Firstly, consider whether BINARY is actually the appropriate field type. When compared to BLOB it has a potentially nasty "feature" of stripping trailing spaces. BINARY is really designed to be just a case-insenstive binary text string, and not a blob of arbitrary binary data.

如果确实使用blob，则需要结合使用SUBSTRING()运算符和ASCII()来提取所需的字节，然后使用|逐位运算符.

If you do use a blob, you'd need to use the SUBSTRING() operator combined with ASCII() to extract just the byte you want, then use the | bitwise operator.

要在第二个字节中设置内容，您需要使用类似以下内容的内容:

To set something in the second byte you'd need to use something like:

UPDATE TABLE SET col = CONCAT(
   SUBSTR(col, 1, 1),
   CHAR(ASCII(SUBSTR(col, 2, 1) | 0x80)),
   SUBSTR(col, 3)
)

一个可能更简单的解决方案是将100个字节视为12.5个64位(即BIGINT)，然后对单个单词使用直接按位运算.

A possibly simpler solution might be to treat your 100 bytes as 12.5 lots of 64 bits (i.e. BIGINT), and then use direct bitwise operations on individual words.

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