整理声明的SQL变量

Question

I've been looking at this code, reproduced below, that looks for non-ASCII characters...

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

and it just strikes me that I'd want to declare a variable for '%[^ !-~]%' COLLATE Latin1_General_BIN instead of writing it out every time, but

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

just doesn't do the same thing. Am I just missing some syntax? Is it impossible?

Answer 1

It is normal. When you create a variable it takes default collation for database.

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

Your string with COLLATE Latin1_General_BIN is implicitly casted to string with your database default collation.

---

For example database is Case-Insensitive . I use your syntax to create case-sensitive one and check metadata of it:

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

LiveDemo

Output:

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

Variables(excluding columns in table variables) do not allow to define collation so there is no syntax like:

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