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 |
|
Mondeo
Constraint Violating Yak Guru
287 Posts |
 Posted - 2010-09-23 : 08:52:48
|
| Hi,I have this querySELECT DISTINCT [type] COLLATE Latin1_General_CI_AS as [type],capid FROM tblPricing UNIONSELECT DISTINCT [type] COLLATE Latin1_General_CI_AS as [type],capid FROM dbPubMatrix..tblNewMatrixSpecialIf both tables contain 'type1',99999 for example will that record only appear once in this query?Thanks |
|
|
Kristen
Test
22859 Posts |
Posted - 2010-09-23 : 12:02:45
|
| Yes. UNION will sort remove duplicates. If you want to keep duplicates (or you know there will not be any) use UNION ALL - which is faster as it doesn't need to Sort/De-dupe the results) |
 |
|
|
Kristen
Test
22859 Posts |
Posted - 2010-09-23 : 12:03:57
|
Probably no point you having DISTINCT on each SELECT, given that the UNION will remove the DUPs too - so potentially you have 3 Sorts & De-dups, whereas one would do  - but that's assuming that SQL won't optimise it to only do one Sort & De-dupe |
|
|
|
|
|
|
Question about duplicates in UNION