Please start any new threads on our new
site at https://forums.sqlteam.com. We've got lots of great SQL Server
experts to answer whatever question you can come up with.
| Author |
Topic |
|
Timmy6
Starting Member
8 Posts |
 Posted - 2009-03-03 : 10:33:32
|
| HiI am currently writing my first proper peice of SQL to manipulate a sizeable data set and need to query 1 table twice and combine the results to create a new tableHowever if I run my first select query I get 59,337 records, i then run my second select query and get 378,474 records. I then apply a union all into the script to compine the 2 select stamtements into a single data set but end up with more records than the 2 numbers above combined!I know that union alone will remove duplicates but I dont understand how union all can increase the number of recordsDoes anyone have any tips on how to error check this, bearing in mind my 2 select statements in isolation seem to be OKThanks |
|
|
sakets_2000
Master Smack Fu Yak Hacker
1472 Posts |
Posted - 2009-03-03 : 10:48:32
|
| not possible. Can you post the unioned statement ?? Also, how did you find out the counts ? |
 |
|
|
SwePeso
Patron Saint of Lost Yaks
30421 Posts |
Posted - 2009-03-03 : 10:50:18
|
UNION alone can double the number of records returned.Post your code here and we will spot the other errors.
E 12°55'05.63"N 56°04'39.26" |
|
|
|
visakh16
Very Important crosS Applying yaK Herder
52326 Posts |
Posted - 2009-03-03 : 10:59:06
|
quote:
Originally posted by Timmy6
HiI am currently writing my first proper peice of SQL to manipulate a sizeable data set and need to query 1 table twice and combine the results to create a new tableHowever if I run my first select query I get 59,337 records, i then run my second select query and get 378,474 records. I then apply a union all into the script to compine the 2 select stamtements into a single data set but end up with more records than the 2 numbers above combined!I know that union alone will remove duplicates but I dont understand how union all can increase the number of recordsDoes anyone have any tips on how to error check this, bearing in mind my 2 select statements in isolation seem to be OKThanks
it would be better if you can explain this with some sample data to illustrate how you get more records in output |
|
|
|
Timmy6
Starting Member
8 Posts |
Posted - 2009-03-03 : 11:27:31
|
| Sorry to waste you guys time but I had duplicate records in my joined table, I had already checked once too!All working as expected now |
|
|
|
|
|
|
Union All