Expression on an Expression alias

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От Mike Ellsworth
Тема Expression on an Expression alias
Дата
Msg-id 219951fd0804181321k3d756da2k8a0198fe73abcfce@mail.gmail.com
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Ответы Re: Expression on an Expression alias  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-novice
I'm wondering if there is a way to write an expression on an
expression alias... or 'build on' an existing expression alias.
I am slowly converting old Filemaker work to PG and the below would be helpful.
My old Filemaker allows something similar to var 2 below.

This is an example ( a little feeble) where FV is a function
the first one works, but can get lengthy if I start to nest variations.

SELECT
fv_test.acct_val AS acct_val,
fv_test.time AS time,
fv_test.i AS interest_rate,
FV(fv_test.acct_val,fv_test.i,fv_test.time) AS FV1,
FV(fv_test.acct_val,fv_test.i,fv_test.time) *2 AS FV2,
FV(fv_test.acct_val,fv_test.i,fv_test.time) *3 AS FV3
FROM    "hrcommu"."fv_test"

The *effect* I'd like is to 'reuse' FV1, ~

SELECT
fv_test.acct_val AS acct_val,
fv_test.time AS time,
fv_test.i AS interest_rate,
FV(fv_test.acct_val,fv_test.i,fv_test.time) AS FV1,
FV1 *2 AS FV2,
FV1 *3 AS FV3
FROM    "hrcommu"."fv_test"

Any suggested reading, would be read.
Thanks

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