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compare 2 large tables

Posted on 2013-05-21
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Last Modified: 2013-05-24
i have 2 tables, lets say:

table1(id bigint) and table2(id bigint)


table1          table2
1                    3
2                    76
23                  89
45                  90
76                  92
90                  98



so i want to select all rows on table1 that does not exist on table2, i have this in place:

 SELECT * FROM TABLE1 AS T1
          WHERE (CASE WHEN EXISTS(SELECT TOP 1 ID FROM TABLE2 WHERE ID = T1.ID) THEN 1 ELSE 0 END) = 0

this query takes a lot from the processor and too hard on my server, both of those tables have about 100000 rows. So i need another better solution to this.
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Question by:rafaelrgl
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7 Comments
 
LVL 11

Expert Comment

by:HuaMinChen
ID: 39186590
1. Make sure you have indices on ID for both tables
2. Try
SELECT * FROM TABLE1 AS T1
          WHERE not EXISTS(SELECT TOP 1 ID FROM TABLE2 t2 WHERE t2.ID = T1.ID);
SELECT * FROM TABLE2 AS t2
          WHERE not EXISTS(SELECT TOP 1 ID FROM TABLE1 t1 WHERE t1.ID = t2.ID);
0
 
LVL 9

Accepted Solution

by:
mimran18 earned 2000 total points
ID: 39186614
CREATE PROCEDURE CompareTables(@table1 varchar(100),
 @table2 Varchar(100), @T1ColumnList varchar(1000),
 @T2ColumnList varchar(1000) = '')
AS
 

declare @SQL varchar(8000);
 
IF @t2ColumnList = '' SET @T2ColumnList = @T1ColumnList
 
set @SQL = 'SELECT ''' + @table1 + ''' AS TableName, ' + @t1ColumnList +
 ' FROM ' + @Table1 + ' UNION ALL SELECT ''' + @table2 + ''' As TableName, ' +
 @t2ColumnList + ' FROM ' + @Table2
 
set @SQL = 'SELECT Max(TableName) as TableName, ' + @t1ColumnList +
 ' FROM (' + @SQL + ') A GROUP BY ' + @t1ColumnList +
 ' HAVING COUNT(*) = 1'
 
exec ( @SQL)

http://weblogs.sqlteam.com/jeffs/archive/2004/11/10/2737.aspx
0
 
LVL 49

Expert Comment

by:PortletPaul
ID: 39186646
select
*
from table1
inner join (
            select ID
            from table1

            except

            select ID
            from table2
           ) cept on table1.id = cept.id

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LVL 10

Expert Comment

by:Asim Nazir
ID: 39186788
If you want to compare data of two tables then you may use Visual Studio's Data/Schema comparison options or even SqlDelta.
0
 
LVL 13

Expert Comment

by:Jitendra Patil
ID: 39186965
as per your given example above,

i've tried to create a small example of except command which can get you near to the results.

DECLARE @Temp1 table (col1 int)
insert into @Temp1(col1)values(1)
insert into @Temp1(col1)values(2)
insert into @Temp1(col1)values(3)
insert into @Temp1(col1)values(4)
insert into @Temp1(col1)values(5)
insert into @Temp1(col1)values(6)

DECLARE @Temp2 table (col1 int)
insert into @Temp2(col1)values(1)
insert into @Temp2(col1)values(4)
insert into @Temp2(col1)values(6)
insert into @Temp2(col1)values(7)
insert into @Temp2(col1)values(4)
insert into @Temp2(col1)values(8)

select * from @Temp1
except
select * from @Temp2


please give  a try & hope this helps.
0
 
LVL 48

Expert Comment

by:Dale Fye
ID: 39187166
SELECT T1.*
FROM Table1 as T1
LEFT JOIN Table2 as T2
ON T1.ID = T2.ID
WHERE T2.ID IS NULL
0
 
LVL 1

Author Closing Comment

by:rafaelrgl
ID: 39190683
this way is really faster compare to the one i was using.
0

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