Db Name as parameter in stored procedure SQL Server - sql

Question

I'm looking to pass my database name as a parameter to the stored procedure, and I'm looking to use it in the where condition to set the database of the stored procedure. But I get an error:
Incorrect syntax near '.'
Sample Code
Create proc [dbo].[stored_procedure_one]
#variable1 int,
#dbname varchar(10)
as
begin
select *
from #dbname..table_name
End
Can someone suggest me how to solve this?

Answer 1

You will need to use dynamic sql for this something like this.....
Create proc [dbo].[stored_procedure_one]
#variable1 int,
#dbname SYSNAME --<-- use appropriate data type for object names
as
begin
DECLARE #Sql NVARCHAR(MAX);
SET #Sql = N' select * from ' + QUOTENAME(#dbname) + N'..table_name'
Exec sp_executesql #Sql
End
Also use QUOTENAME() function to protect yourself against possible sql-injection attack.

Answer 2

Just to offer an alternative, it's fun to note that EXEC can take a string as the thing to execute, so for example:
DECLARE #sp nvarchar(255) = N'sys.sp_who2';
EXEC #sp;
It can also take parameters, e.g.
DECLARE #sp nvarchar(255) = N'sys.sp_who2';
EXEC #sp 'active';
So we can dynamically build the context where we run a command by using:
DECLARE #dbname sysname = N'tempdb';
DECLARE #context nvarchar(1000) = QUOTENAME(#dbname)
+ N'.sys.sp_executesql';
DECLARE #sql nvarchar(max) = N'SELECT DB_NAME();';
EXEC #context #sql;
And you can pass parameters, too:
DECLARE #dbname sysname = N'tempdb';
DECLARE #context nvarchar(1000) = QUOTENAME(#dbname)
+ N'.sys.sp_executesql';
DECLARE #sql nvarchar(max) = N'SELECT DB_NAME(), #x;';
EXEC #context #sql, N'#x int', 5;
This approach really simplifies things like concatenating the database name all over the place, avoiding db-specific functions like object_name, and ensures that your entire command runs in that other database. You can also do it across linked servers, e.g.:
DECLARE #server sysname = N'linked_server';
DECLARE #dbname sysname = N'tempdb';
DECLARE #context nvarchar(1000) = QUOTENAME(#server)
+ N'.' + QUOTENAME(#dbname)
+ N'.sys.sp_executesql';
...