Why is the table inside a non-met IF being validated before condition is met, resulting in error if table does not exist?

Question

I am trying to execute a procedure with a parameter, and depending on the value of the parameter, three different IF conditions will be evaluated to verify which query it will execute from a linked server.

But when I execute the query, it seems to be checking if the tables inside all the IF exists before starting the query. And I know that only one of the table exists, that is why I am using the parameter, so it shouldn't fail. but I anyhow get the following error:

Msg 7314, Level 16, State 1, Line 25 The OLE DB provider "Microsoft.ACE.OLEDB.16.0" for linked server "LinkedServer" does not contain the table "D100". The table either does not exist or the current user does not have permissions on that table.

So in this code, assume that the parameter is 300. then I get the message above. Do you know, if there is a way, to limit the query to do not check all the tables, but only the one where the IF condition will be met?

ALTER PROCEDURE[dbo].[Import_data]
@p1 int = 0
AS
BEGIN
    SET NOCOUNT ON;

    IF(@p1 = 100)
    BEGIN
        DROP TABLE IF EXISTS Table1
        SELECT [Field1], [Field2], [Field3], [Field4], [Field5], [Field6]
        INTO Table1
        FROM[LinkedServer]...[D100]
    END

    IF(@p1 = 200)
    BEGIN
        DROP TABLE IF EXISTS Table2
        SELECT[Field1], [Field2], [Field3], [Field4], [Field5], [Field6]
        INTO Table2
        FROM[LinkedServer]...[D200]
    END

    IF(@p1 = 300)
    BEGIN
        DROP TABLE IF EXISTS Table3
        SELECT[Field1], [Field2], [Field3], [Field4], [Field5], [Field6]
        INTO Table3
        FROM[LinkedServer]...[D300]
    END
END

I have tried googling it, but I found mostly workarounds as running a sub procedure, but it is not really a clean solution, I think.

Answer 1

Okay, it seems I that I found the answer. Even with an IF statement, the SQL Server validates the entire query before executing it, so the way to overcome it, is to use a Dynamic SQL Query.

"SQL Server Dynamic SQL is a programming technique that allows you to construct SQL statements dynamically at runtime. It allows you to create more general purpose and flexible SQL statement because the full text of the SQL statements may be unknown at compilation."

This is how the query looks now. so instead of multiple IF statements, the query changes dynamically depending on the parameter.

    DECLARE @SQL NVARCHAR(MAX)
    SET @SQL = N'DROP TABLE IF EXISTS Table1; 
                SELECT [Field1]
                    ,[Field2]
                    ,[Field3]
                    ,[Field4]
                    ,[Field5]
                    ,[Field6]
                INTO Table1
            FROM [LinkedServer]...[D' + CONVERT(nvarchar(3),@p1) + N']'
    EXEC sp_executesql @SQL