Comparing two T-SQL tables for diffs

Question

I have two instances of the same database. The first db represents data from today, the second data from 6 months ago. I need to find differences for a subset of entries in a specific table.

For entries with ids that are in both tables, I'd like to find a way to view only the rows that aren't identical.

Any ideas?

Thanks

Answer 1

You can use the TableDiff.exe utility that comes with SQL Server 2005 and above.

You can read more here.

Answer 2

SELECT t1.id
FROM table1 t1
INNER JOIN table2 t2 ON t1.id = t2.id
WHERE ISNULL(t1.field1,'') <> ISNULL(t2.field1,'')
      OR ISNULL(t1.field2,'') <> ISNULL(t2.field2,'')
      OR ...

To produce long WHERE part you can use this function:

CREATE PROCEDURE compareTables
    @db1    NVARCHAR(100),
    @table1 NVARCHAR(100),
    @db2    NVARCHAR(100),
    @table2 NVARCHAR(100)
AS
BEGIN
    SET NOCOUNT ON;
    DECLARE @where NVARCHAR(MAX)
    DECLARE @cmd NVARCHAR(MAX)

    SET @where = ''

    SELECT @where = @where + 'ISNULL(t1.' + name + ','''') <> ISNULL(t2.' + name + ','''') OR ' 
    FROM sys.columns WHERE object_id = OBJECT_ID(@table1)

    SET @where = SUBSTRING(@where,1,LEN(@where)-3)

    SET @cmd = 'SELECT t1.id FROM ' + @db1 + '.' + @table1 + ' t1 '
    SET @cmd = @cmd + 'INNER JOIN ' + @db2 + '.' + @table2 + ' t2 ON t1.id = t2.id '
    SET @cmd = @cmd + 'WHERE ' + @where

    EXEC sp_executesql @cmd
END
GO

Example usage:

EXEC compareTables 'db1_name','dbo.table1','db2_name','dbo.table1'

Remember to put schema in the table name.

Answer 3

for SQL Server 2005 and up try something like this:

declare @CurrentTable table (pk int, valuedata varchar(5))
declare @oldtable table (pk int, valuedata varchar(5))

insert into @CurrentTable values (1,'aa')
insert into @CurrentTable values(2,'bb')
insert into @CurrentTable values(3,'cc')
insert into @CurrentTable values(4,'dd')
insert into @CurrentTable values(5,'ee')

insert into @oldtable values(1,'aa')
insert into @oldtable values(1,'bb')
insert into @oldtable values(3,'zz')
insert into @oldtable values(7,'aa')
insert into @oldtable values(8,'qq')

select pk,valuedata  from @CurrentTable
except
select pk,valuedata from @oldtable

OUTPUT

pk          valuedata
----------- ---------
2           bb
3           cc
4           dd
5           ee

(4 row(s) affected)

if SQL Server 2000 or older try something like this:

SELECT
    c.*
    FROM YourTableCurrent             c
        LEFT OUTER JOIN YourTableOld  o ON c.id=o.id
    WHERE ISNULL(c.IntCol,-2147483648)!=ISNULL(o.IntCol,-2147483648)
        OR ISNULL(c.varcharCol,'||null||')!=ISNULL(o.varcharCol,'||null||')
        OR ISNULL(c.DatetimeCol,'01/01/1753')!=ISNULL(o.DatetimeCol,'01/01/1753')
        ....
UNION
SELECT
    o.*
    FROM YourTableOld                     o
        LEFT OUTER JOIN YourTableCurrent  c ON c.id=o.id
    WHERE c.id IS NULL
        ....

Answer 4

From your text, I think you say there is an ID that can be used for matching rows.

SELECT t1.*, t2.*
FROM table1 t1 JOIN table2 t2 ON t1.id=t2.id 
WHERE BINARY_CHECKSUM(t1.*) <> BINARY_CHECKSUM(t2.*)

Untested, but should work.

Answer 5

Just so you are aware, there is a terrific third party tool that you can buy to do this sort of thing for SQL Server databases called SQL Data Compare. It is sold by red-gate. http://www.red-gate.com/products/SQL%5FData%5FCompare/index.htm?gclid=CKPp-6-Bi50CFQRM5QodtWGl8g

There's a free trial. But it's worth spending the money for.

Answer 6

A bit late, but:

SELECT *
 from Table1
except select *
 from Table2

will list all rows in Table1 that are not present in Table2,

SELECT *
 from Table2
except select *
 from Table1

will show all in Table2 that are not in Table1, and

SELECT *
 from Table1
intersect select *
 from Table2

will show all rows that are identical in both tables. If any colums are known to vary between tables, specify only those columns you need to compare.