Sql-server – What happens during “big” inserts on a table with a clustered composite key

You can also do this with dynamic SQL without having to manually build out all the column names.

DECLARE @sql NVARCHAR(MAX), @c1 NVARCHAR(MAX), @c2 NVARCHAR(MAX);

SELECT @c1 = N'', @c2 = N'';

SELECT 
  @c1 = @c1 + ',' + QUOTENAME(name),
  @c2 = @c2 + ' AND m.' + QUOTENAME(name) + ' = s.' + QUOTENAME(name)
 FROM sys.columns
 WHERE name <> 'LocationID'
 AND [object_id] = OBJECT_ID('dbo.table1');

SET @sql = ';WITH s AS (
       SELECT ' + STUFF(@c1, 1, 1, '') + ' FROM dbo.table1
       EXCEPT 
       SELECT ' + STUFF(@c1, 1, 1, '') + ' FROM dbo.table1_master
     ) 
     SELECT m.LocationID
 FROM s INNER JOIN dbo.table1 AS m ON 1 = 1
 ' + @c2;

SELECT @sql;
--EXEC sp_executesql @sql;

You can take the output of this query as is and store the query somewhere, or you can comment out the SELECT and uncomment the EXEC and leave it as permanent dynamic SQL - in this case it will automatically adapt to column changes in the two tables.

Another idea (assuming LocationID is unique) - and it occurred to me you may want to include the master row so you can quickly spot the columns that are different:

  ;WITH c AS 
  (
    SELECT t.LocationID, m.setting1, m.setting2, ...
      FROM dbo.table1 AS t CROSS JOIN dbo.table1_master AS m
  )
  SELECT DISTINCT src = '> master', setting1, setting2, ...
    FROM c
  UNION ALL
  (
    SELECT RTRIM(LocationID), setting1, setting2, ...
      FROM dbo.table1
    EXCEPT
    SELECT RTRIM(LocationID), setting1, setting2, ...
      FROM c
  )
  ORDER BY src;

This version is a little cheaper (mostly by avoiding the DISTINCT against the master table, at the cost of needing to specify all of the columns one more time - which again you can automate as per above):

  ;WITH m AS 
  (
    SELECT setting1, setting2, ... 
      FROM dbo.table1_master
  ),
  c AS 
  (
    SELECT src = RTRIM(t.LocationID), m.setting1, m.setting2, ...
      FROM dbo.table1 AS t CROSS JOIN m
  )
  SELECT src = '> master', setting1, setting2, ...
    FROM m
  UNION ALL
  (
    SELECT RTRIM(LocationID), setting1, setting2, ...
      FROM dbo.table1
    EXCEPT
    SELECT src, setting1, setting2, ...
      FROM c
  )
  ORDER BY src;

However all of these options are poorer performers with worse plans than Rachel's simple LEFT JOIN. I tried to stick to the theme of using EXCEPT even though it is more about syntax than performance.

The key takeaway is that if the column count is too high to deal with manually, you can use the dynamic SQL approach above to construct whatever query you want to use - and you can do that one time and store the result, or have the code generated every time. To generate Rachel's query using dynamic SQL, not much needs to change:

DECLARE @sql NVARCHAR(MAX), @and NVARCHAR(MAX), @anycol NVARCHAR(128);
SELECT @sql = N'', @and = N'';

SELECT @and = @and + ' AND t.' + QUOTENAME(name) + ' = m.' + QUOTENAME(name)
  FROM sys.columns
  WHERE [object_id] = OBJECT_ID('dbo.table1_master');

SELECT TOP (1) @anycol = QUOTENAME(name)
  FROM sys.columns
  WHERE [object_id] = OBJECT_ID('dbo.table1_master')
  ORDER BY name;

SET @sql = 'SELECT locationID
FROM dbo.table1 AS t
LEFT OUTER JOIN dbo.table1_master AS m ON 1 = 1' 
  + @and + ' WHERE m.' + @anycol + ' IS NULL;';

SELECT @sql;
--EXEC sp_executesql @sql;

Instead of:

ALTER TABLE Donations ADD FOREIGN KEY(EventID) REFERENCES Events(ID)
ALTER TABLE Donations ADD FOREIGN KEY(LocationID) REFERENCES Locations(ID)

I would do this:

ALTER TABLE Donations ADD FOREIGN KEY(EventID) REFERENCES Events(ID)
ALTER TABLE Donations ADD FOREIGN KEY(EventID, LocationID) REFERENCES Locations(EventID, ID)

That would guarantee that "if the LocationID is specified, then that LocationID should be a Location that belongs to the specified EventID".

That done, your approach makes sense.