sql - Replace Placeholder with Value from other table

Question

Let say I have a stored procedure that will insert record into table1

INSERT INTO tbl_table1 (Id, Parameter)
Select Id, Parameter
FROM tbl_table2

And example for table2 and table3 as below:

tbl_table2 - Not every field has Parameter

Id	Field	Parameter
1	Field1	A = [As_Of_Date], B = [itemType]
2	Field2	NULL

Answer 1

If I understand your intent correctly, then you want to insert Id from table2 and Parameter from table3 which is a join in the SELECT statement:

INSERT INTO table1( Id, Parameter)
SELECT 
  tbl2.Id,
  tbl3.Parameter
FROM
  table2 AS tbl2
  -- link to result
  INNER JOIN table3 AS tbl3
    ON  tbl3.Id = tbl2.Id
;

Is this good enough?