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I wonder whether the query optimizer will eliminate redundant calls of the function?
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I wonder whether the query optimizer will eliminate redundant calls of the function?

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Sure it will, as long as they are written identically.
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Sure it will, as long as they are written identically.

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In Sybase adaptive server 11, the following gave me 'invalid column name mnth'. How can I summarize sales by month?<br />
<br />
select sum( subtotal ) as sales_summary,<br />
&nbsp; datediff ( mm, &nbsp;'Jan 1 2000', order_date ) as mnth<br />
from sales_order<br />
where mnth &gt;&nbsp;0<br />
group by mnth<br />

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In Sybase adaptive server 11, the following gave me 'invalid column name mnth'. How can I summarize sales by month?

select sum( subtotal ) as sales_summary,
  datediff ( mm,  'Jan 1 2000', order_date ) as mnth
from sales_order
where mnth > 0
group by mnth


group by a computed column didn't work in sybase. why?

Sybase, a subsidiary of SAP, builds a client/server relational database management system. Products include Adaptive Server Enterprise (ASE), Adaptive Server Anywhere (ASA), Sybase Unwired Platform (SUP) for mobile applications, Afaria for enterprise mobile device management and IQ for data warehouse and big data applications.