2005-01-28 15:07:11 +01:00
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ROWS clause
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Function:
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Allow to limit a number of rows retrieved from a select expression. For a highest level
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select statement, it would mean a number of rows sent to the host program.
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Author:
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Dmitry Yemanov <yemanov@yandex.ru>
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Syntax rules:
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SELECT ... [ORDER BY <expr_list>] ROWS <expr1> [TO <expr2>]
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Scope:
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DSQL, PSQL
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Example(s):
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1. SELECT * FROM T1
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UNION ALL
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SELECT * FROM T2
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ORDER BY COL
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ROWS 10 TO 100
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2. SELECT COL1, COL2, ( SELECT COL3 FROM T3 ORDER BY COL4 DESC ROWS 1 )
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FROM T4
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3. DELETE FROM T5
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ORDER BY COL5
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ROWS 1
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Note(s):
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1. ROWS is a more understandable alternative to the FIRST/SKIP clauses with some extra benefits.
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It can be used in unions and all kind of subqueries. Also it's available in the UPDATE/DELETE
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statements.
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2. When <expr2> is omitted, then ROWS <expr1> is a semantical equivalent for FIRST <expr1>. When
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both <expr1> and <expr2> are used, then ROWS <expr1> TO <expr2> means:
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FIRST (<expr2> - <expr1> + 1) SKIP (<expr1> - 1). Note that there's no semantical equivalent
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for a SKIP clause used without a FIRST clause.
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