整理声明的 SQL 变量

我一直在看查找非 ASCII 字符的查询 https://stackoverflow.com/a/3917698/241211，转载如下……

select line,
  patindex('%[^ !-~]%' COLLATE Latin1_General_BIN, Line) as [Position],
  substring(Line, patindex('%[^ !-~]%' COLLATE Latin1_General_BIN, Line), 1) as [InvalidCharacter],
  ascii(substring(line, patindex('%[^ !-~]%' COLLATE Latin1_General_BIN, Line), 1)) as [ASCIICode]
from staging.APARMRE1
where patindex('%[^ !-~]%' COLLATE Latin1_General_BIN, Line) > 0

...我突然想到我想声明一个变量'%[^ !-~]%' COLLATE Latin1_General_BIN而不是每次都写出来，但是

declare @regex varchar(20) = '%[^ !-~]%' COLLATE Latin1_General_BIN;

select line,
  patindex(@regex, Line) as [Position],
  substring(Line, patindex(@regex, Line), 1) as [InvalidCharacter],
  ascii(substring(line, patindex(@regex, Line), 1)) as [ASCIICode]
from staging.APARMRE1
where patindex(@regex, Line) > 0

只是不做同样的事情。我只是缺少一些语法吗？难道不可能吗？

这是正常的。创建变量时，它采用数据库的默认排序规则。

DECLARE @regex varchar(20) = '%[^ !-~]%' COLLATE Latin1_General_BIN;

你的字符串与COLLATE Latin1_General_BIN is 隐式投射使用数据库默认排序规则进行字符串化。

DECLARE @v1 varchar(100) = 'ABC' COLLATE Latin1_General_CS_AS;

SELECT name, collation_name
FROM sys.dm_exec_describe_first_result_set(
    N'SELECT @v1 AS [@v1]', N'@v1 varchar(100)', 0);

LiveDemo https://data.stackexchange.com/stackoverflow/query/403728

Output:

╔══════╦══════════════════════════════╗
║ name ║        collation_name        ║
╠══════╬══════════════════════════════╣
║ @v1  ║ SQL_Latin1_General_CP1_CI_AS ║
╚══════╩══════════════════════════════╝

变量（不包括表变量中的列）不允许定义排序规则，因此没有如下语法：

DECLARE @v1 varchar(100) COLLATE Latin1_General_CS_AS = 'ABC' ;
-- Incorrect syntax near the keyword 'COLLATE'.