问题
When i read the example of MSDN raiserror:
RAISERROR (N'This is message %s %d.', -- Message text.
10, -- Severity,
1, -- State,
N'number', -- First argument.
5); -- Second argument.
-- The message text returned is: This is message number 5.
GO
Why the doc using %s to specify the N'number',and %d to specify the 5 -- Second argument
The MSDN write like this:
For example, in the following RAISERROR statement, the first argument of N'number' replaces the first conversion specification of %s; and the second argument of 5 replaces the second conversion specification of %d.
My question is: How can explain it? Why don't using other like %a or %b.Any other %+apha can replace it.
I just want to get a meaningful understand.
回答1:
This represents the parameter datatype.
+--------------------+----------------------+
| Type specification | Represents |
+--------------------+----------------------+
| d or i | Signed integer |
| o | Unsigned octal |
| s | String |
| u | Unsigned integer |
| x or X | Unsigned hexadecimal |
+--------------------+----------------------+
N'number' is an nvarchar string literal. So gets the %sspecifier. And the literal 5 is a signed indicator so is represented by %d.
As for the reason for these specifiers. This is documented in the RAISERROR topic
These type specifications are based on the ones originally defined for the printf function in the C standard library
来源：https://stackoverflow.com/questions/19477547/sql-raiserror-specify-parameter