Dmitry Yemanov <[email protected]> писал(а) в своём письме Thu, 02 Jan
2014 15:55:57 +0400:
>
> This makes it necessary to allow the FIRST ROWS mode when it's needed.
> I'm proposing the following:
>
> 1) FIRST ROWS mode is implicitly used when the FIRST / ROWS clause is in
> game. Also, FIRST ROWS mode is implicitly used for EXISTS / ANY
> subqueries.
>
> 2) An explicit clause is introduced to force the non-default mode (ALL
> ROWS for FIRST-claused queries and FIRST ROWS for other queries). Hating
> Oracle-like pseudo-comments with embedded hints and preferring explicit
> syntax, I suggest (inspired by DB2):
>
> SELECT ...
> [OPTIMIZE FOR {FIRST | ALL} ROWS]
>
Syntax for tips aka DB2 I like more, but it reduces the portability of SQL
queries themselves between different DBMS, while syntax Oracle (as a
comment) does not have this disadvantage. If all the tips are localized in
one place it may slightly alleviate this problem.
About the default optimization as ALL ROWS fully agree.
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