Hallo Andreas,
I reduced the problem to the innermost query:
1) SELECT DISTINCT trainer_id, trainer_name FROM student
This results in a sequential table scan. Execution time 7500ms.
2) I created an INDEX ON (trainer_id, trainer_name). Then I had an index
scan instead, which still cost 7000ms.
;>> From: "Tarlika Elisabeth Schmitz"
>>> To:
>>> Sent: Monday, September 27, 2010 5:54 PM
>>> Subject: Re: [SQL] identifying duplicates in table with redundancies
>>>
>>>
>>>> On Fri, 24 Sep 2010 18:12:18 +0100
>>>>
On 09/28/2010 10:36 PM, Tarlika Elisabeth Schmitz wrote:
On Tue, 28 Sep 2010 11:34:31 +0100
"Oliveiros d'Azevedo Cristina" wrote:
- Original Message -
From: "Tarlika Elisabeth Schmitz"
To:
Sent: Monday, September 27, 2010 5:54 PM
Subject: Re: [SQL] identi
On Tue, 28 Sep 2010 11:34:31 +0100
"Oliveiros d'Azevedo Cristina" wrote:
>- Original Message -
>From: "Tarlika Elisabeth Schmitz"
>To:
>Sent: Monday, September 27, 2010 5:54 PM
>Subject: Re: [SQL] identifying duplicates in table with redundan
answer.
There are many people on this list that can help you better
Best,
Oliveiros
- Original Message -
From: "Tarlika Elisabeth Schmitz"
To:
Sent: Monday, September 27, 2010 5:54 PM
Subject: Re: [SQL] identifying duplicates in table with redundancies
On Fri, 24 Sep 2
On Fri, 24 Sep 2010 18:12:18 +0100
Oliver d'Azevedo Christina wrote:
>>> SELECT DISTINCT trainer_id,trainer_name
>>> FROM (
>>> SELECT trainer_name -- The field you want to test for duplicates
>>> FROM (
>>> SELECT DISTINCT "trainer_id","trainer_name"
>>> FROM student
>>> ) x
>>> GROUP BY "trai
Hello Oliveiros,
On Fri, 24 Sep 2010 18:12:18 +0100
Oliver d'Azevedo Christina wrote:
>Hey,Tarlika.
>I tried to reproduce your test case through a series of inserts and
>It seems that the lower case "d" went unnoticed.
I can assure you people up here (in Scotland) get quite upset about it!
It
t: Thursday, September 23, 2010 10:39 PM
Subject: [SQL] identifying duplicates in table with redundancies
[...] I want to check for duplicates:
1) multiples trainer names for same trainer id
2) multiple trainer ids for same trainer name
I cobbled together the SQL and it does the job but it see
Dear Oliveiros,
Thank you for taking the time to help.
On Fri, 24 Sep 2010 11:22:21 +0100
"Oliveiros d'Azevedo Cristina" wrote:
>- Original Message -
>From: "Tarlika Elisabeth Schmitz"
>To:
>Sent: Thursday, September 23, 2010 10:39 PM
>Subjec
er_id on
the commented places.
But on the example data you provided you don't have the 1) situation, am I
right? So it will output an empty list.
Best,
Oliver
- Original Message -
From: "Tarlika Elisabeth Schmitz"
To:
Sent: Thursday, September 23, 2010 10:39 PM
Subj
I loaded data from a spread into a interim table so I can analyze the
quality of the data.
The table contains an entry for every student (250K records) and his
trainer. Eventually, I want to extract a unique list of trainers from
it. But first of all I want to check for duplicates:
1) multiples t
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