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42 lines
1.3 KiB
Plaintext
42 lines
1.3 KiB
Plaintext
-----------
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ROWS clause
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-----------
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Function:
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Limits the number of rows retrieved from a select expression. For the
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top-level select statement, it would mean a number of rows sent to the host
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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
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some extra benefits. It can be used in unions and all kind of subqueries.
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It is also available in the UPDATE/DELETE statements.
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2. When <expr2> is omitted, then ROWS <expr1> is a semantical equivalent for
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FIRST <expr1>. When both <expr1> and <expr2> are used, then ROWS <expr1>
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TO <expr2> means:
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FIRST (<expr2> - <expr1> + 1) SKIP (<expr1> - 1). Note that there's no
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semantic equivalent for a SKIP clause used without a FIRST clause.
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3. The ROWS-clause is not defined in the SQL standard. For SELECT, consider
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the alternative OFFSET and FETCH clauses defined in the SQL standard.
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