Consecutive row count query

From: Leon Stringer <leon(dot)stringer(at)ntlworld(dot)com>
To: pgsql-sql(at)postgresql(dot)org
Subject: Consecutive row count query
Date: 2005-03-17 20:21:24
Message-ID: 1111090884.22783.5.camel@localhost.localdomain
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Hi,

I wondered if anyone could answer the following question:

If I have a table such as the one below:

col1 col_order
-----------
Apple 1
Apple 2
Orange 3
Banana 4
Apple 5

Is there a way I can get the following results:

Apple 2
Orange 1
Banana 1
Apple 1

i.e. Each row is printed ordered by col_order but consecutive
appearances of the same col1 result in only a single line in the result
with the number of consecutive appearances.

Obviously I could store the table as:

col1 col_order col_count
--------------------------
Apple 1 2
Orange 2 1
Banana 3 1
Apple 4 1

But since (in my intended table) most rows will have col_count = 1, this
seems like unnecessary normalization (and semantically "wrong").

Thanks in advance for any help,

Leon Stringer

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