字符串和变量 SQL 的串联

Question

SET @Result = '{ "host_name": "' + @hostname + '", "status": 15 }'

Could you explain to me what we get with the value of Result please? If we assume that hostname = "machine1".

To test this, I created a table and a Stored Procedure and Print the value of Result :

CREATE TABLE utilisateur
(
    
    nom VARCHAR(100),
    prenom VARCHAR(100),    
    age VARCHAR(5),
    
)
INSERT INTO utilisateur (prenom, nom, age)
 VALUES
 ('Rébecca', 'Armand', 24)
go

 CREATE PROCEDURE [sp_DB] 
  @hostname nvarchar(50),
  @Result nvarchar(2000) OUTPUT

AS
  select age as a from utilisateur where nom = 'Armand' 
  SET @hostname = 'machine1'
  SET @Result = '{ "host_name": "' + @hostname + '", "a": 15 }' 
  print @Result

EXEC [sp_DB]@hostname ='machine1',@Result = 'test';

But the execution does not display the content of the Result variable.

PS : I use sqlfiddle.com/ to execute the code

Answer 1

You have to define the output variable on the procedure calling scope, and use the keyword OUTPUT to retrieve output the value. So if you do it like:

declare @result_out nvarchar(2000)
EXEC [sp_DB]@hostname ='machine1',@Result=@result_out OUTPUT;
select @result_out as [Result]

It will work.