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| WEBDEV19 - How to Code SQL, 2 files, only bring back Unique |
| Iniciado por guest, 22,jul. 2015 00:23 - 6 respuestas |
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| Publicado el 22,julio 2015 - 00:23 |
Hi all -
I'm not very good at SQL, so rather than spend hours trying to figure this one out on my own, I figured I'd ask for help first.
I have 2 files, both have a ContactID field in them. I want to create a single list of ContactID's - without any duplicates in them. So basically if a contact shows up in either of these files, I want to work with them.
Any have some code to get me started? I don't know anything about inner / outer joins (other than they exist) |
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| Publicado el 22,julio 2015 - 01:16 |
Out of the mind and not tested:
Select table1.customerID
UNION
Select table2.customerID
should do a distinct select
Select table1.customerID
UNION ALL
Select table2.customerID
should be with duplicates |
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| Publicado el 22,julio 2015 - 01:17 |
Correction:
Select table1.customerID from table1
UNION
Select table2.customerID from table2 |
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| Publicado el 22,julio 2015 - 02:26 |
I'd suggest a slight change...
SELECT DISTINCT table1.customerID from table1
UNION
SELECT DISTINCT table2.customerID from table2 |
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| Publicado el 22,julio 2015 - 02:59 |
| But if the same ContactID is in both files, after you do the union, wouldn't it show up twice in the final file? |
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| Publicado el 22,julio 2015 - 11:11 |
Hi Joel,
No the ContactID wouldn't show up twice. This is the difference between UNION and UNION ALL.
UNION - removes duplicates
UNION ALL - keeps duplicates
Thanks
Ned! |
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| Publicado el 22,julio 2015 - 14:26 |
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