SQL Server WHERE子句中的“&"运算符 [英] Ampersand (&) operator in a SQL Server WHERE Clause

问题描述

很抱歉，这是一个非常基本的问题.& 运算符在此SQL中做什么

Sorry for the very basic question. What does the & operator do in this SQL

WHERE (sc.Attributes & 1) = 0 

sc 是表的别名，该表包含列属性.

sc is an alias for a table which contains a column attributes.

我试图了解报表中的某些SQL，并且该行使其返回0个条目.如果我将其注释掉，它将起作用.我对SQL的了解有限，我不确定&是什么.1 正在执行.

I'm trying to understand some SQL in a report and that line is making it return 0 entries. If I comment it out it works. I have limited SQL knowledge and I'm not sure what the & 1 is doing.

推荐答案

&是按位逻辑和运算符-它对2个整数值执行运算.

& is the bitwise logical and operator - It performs the operation on 2 integer values.

WHERE (sc.Attributes & 1) = 0 

上面的代码检查sc.Attributes是否为偶数.这与说未设置第一位相同.

The above code checks to see if sc.Attributes is an even number. Which is the same as saying that the first bit is not set.

由于该列的名称为:"Attributes"，因此"1"值可能只是一些具有某些外部含义的标志.

Because of the name of the column though: "Attributes", then the "1" value is probably just some flag that has some external meaning.

对于存储在属性编号中的每个标志，通常使用1个二进制数字.因此，要测试第一位，请使用sc.Attributes& 1，测试第二位，请使用sc.Attributes& 2，测试第三位，请使用sc.Attributes& 4，测试第四位，请使用sc.属性& 8，...

It is common to use 1 binary digit for each flag stored in a number for attributes. So to test for the first bit you use sc.Attributes&1, to test for the second you use sc.Attributes&2, to test for the third you use sc.Attributes&4, to test for the fourth you use sc.Attributes&8, ...

= 0部分正在测试以查看是否未设置第一位.

The = 0 part is testing to see if the first bit is NOT set.

一些二进制示例:(==显示操作结果)

Some binary examples: (== to show the result of the operation)

//Check if the first bit is set, same as sc.Attributes&1
11111111 & 00000001 == 1
11111110 & 00000001 == 0
00000001 & 00000001 == 1


//Check if the third bit is set, same as sc.Attributes&4
11111111 & 00000100 == 1
11111011 & 00000100 == 0
00000100 & 00000100 == 1

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