CODEWITHSUNDEEP
sql
ido horowitz
ido horowitz

Reputation: 3

Querying 2 tables for all results

I have a sql qustion. its suppose to be simple but i cant figure it out. I have 2 tables:

**customer1 -** 
id      name
1       aaa
2       bbb
3       ccc
4       ddd

**customer2**-
id      name
1       aaa
2       bbb
5       eee
6       fff

I need to get ALL the customers in both tables. i need to query in a way that if a customer is on both tables I will see him twice in the results (e.g aaa, bbb), and all the rest only one.

Thanks a lot.

Upvotes: 0

Views: 32

Answers (3)

xQbert
xQbert

Reputation: 35333

I would have put this as a comment to : Raghavendra Kedlaya post; but it wouldn't let me.

I like to know from whence the data came when using union all..

SELECT id, name, 'Customer1' as src 
FROM customer1 
UNION ALL 
SELECT id, name, 'Customer2' as src
FROM customer2

Upvotes: 0

Frank
Frank

Reputation: 881

Pay attention to UNION and UNION ALL , with the first one you will not get duplicate , with the second one you will get even duplicate as result of your query.

Let's talk about the performance : A UNION is highly optimized and really fast, except in cases where one query finishes long before the other, and you have to wait to get the whole result set.

When you don't mind about duplicates , UNION ALL will be faster.

Upvotes: 1

Raghavendra Kedlaya
Raghavendra Kedlaya

Reputation: 116

select id, name from customer1
union all
select id, name from customer2

Upvotes: 2

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