Insert rows not contained in one table to another

Question

I have two nearly identical tables, but for a difference of about 100 rows (out of 150k). I know how to find all the rows that exist in one table but not the other by using

SELECT [Column]
FROM [DB].[dbo].[Table_1] 
WHERE NOT EXISTS 
(SELECT * 
 FROM [DB].[dbo].[Table_1a] 
 WHERE [EDB].[dbo].[Table_1a].[Column] = [DB].[dbo].[Table_1].[Column])

But I want to be able to insert the rows missing from Table_1 into Table_1a , but the above code doesn't work in an insert statement:

INSERT [DB].[dbo].[Table_1] 
SELECT *
FROM [DB].[dbo].[Table_1a]
WHERE NOT EXISTS 
    (SELECT * 
     FROM [DB].[dbo].[Table_1a] 
     WHERE [DB].[dbo].[Table_1a].[Column] = [DB].[dbo].[Table_1].[Column])

As I get the error: The multi-part identifier "DB.dbo.Table_1.Column" could not be bound.

I have looked into that error from The multi-part identifier could not be bound and http://www.sql-server-helper.com/error-messages/msg-4104.aspx but neither of those solve my problem as I am not using JOIN or aliases. So, I am not particularly sure what to do.

I am using SQL Server 2017.

Answer 1

You can get all the rows from [DB].[dbo].[Table_1a] that do not exist in [DB].[dbo].[Table_1a] , by using left join:

INSERT [DB].[dbo].[Table_1] 
  SELECT t1a.*
  FROM [DB].[dbo].[Table_1a] t1a
  LEFT JOIN [DB].[dbo].[Table_1] t1
  ON t1a.[Column] = t1.[Column]
  WHERE t1.[Column] IS NULL

Answer 2

The problem is you have two FROM clause references to [DB].[dbo].[Table_1a] and you have not aliased them.

So in the WHERE clause of the subquery (which has access to both the inner and outer queries, and therefore to both occurrences of [DB].[dbo].[Table_1a] ) the optimizer doesn't know which one you mean here:

WHERE [DB].[dbo].[Table_1a].[Column] = ...

If you give two different aliases to those table references, and pick one in the WHERE clause, you should be fine:

INSERT [DB].[dbo].[Table_1] 
SELECT *
FROM [DB].[dbo].[Table_1a] t1
WHERE NOT EXISTS 
    (SELECT * 
     FROM [DB].[dbo].[Table_1a] t2
     WHERE t2.[Column] = [DB].[dbo].[Table_1].[Column])

EDIT:

Another problem is that you are inserting into Table_1 the records in Table_1a WHERE there does not exist a record in Table_1a that matches a record in Table_1 .

This doesn't make much sense. Probably what you meant to do is insert the 1a records that do not already exist in 1 . So probably what you meant is this, which works fine:

INSERT INTO Table_1
SELECT * FROM Table_1a t2
WHERE NOT EXISTS(
    SELECT * FROM Table_1 t1
    WHERE t1.Col1=t2.Col1
)