Firebird 2.1 Language Reference Update

ROWS [TO ]
DML statements
::= The usual output column specifications.
, ::= Any expression evaluating to an integer.
With a UNION:
SELECT [FIRST p] [SKIP q] FROM ...
[WHERE ...]
[ORDER BY ...]
UNION [ALL | DISTINCT]
SELECT [FIRST r] [SKIP s] FROM ...
[WHERE ...]
[ORDER BY ...]
ROWS [TO ]
With a single argument m, the first m rows of the dataset are returned.
Points to note:
• If m > the total number of rows in the dataset, the entire set is returned.
• If m = 0, an empty set is returned.
• If m < 0, an error is raised.
With two arguments m and n, rows m to n of the dataset are returned, inclusively. Row numbers are 1-based.
Points to note when using two arguments:
• If m > the total number of rows in the dataset, an empty set is returned.
• If m lies within the set but n doesn't, the rows from m to the end of the set are returned.
• If m < 1 or n < 1, an error is raised.
• If n = m-1, an empty set is returned.
• If n < m-1, an error is raised.
The SQL-compliant ROWS syntax obviates the need for FIRST and SKIP, except in one case: a SKIP without
FIRST, which returns the entire remainder of the set after skipping a given number of rows. (You can often “fake
it” though, by supplying a second argument that you know to be bigger than the number of rows in the set.)
You cannot use ROWS together with FIRST and/or SKIP in a single SELECT statement, but is it valid to use one
form in the top-level statement and the other in subselects, or to use the two syntaxes in different subselects.
When used with a UNION, the ROWS subclause applies to the UNION as a whole and must be placed after
the last SELECT. If you want to limit the output of one or more individual SELECTs within the UNION, you
have two options: either use FIRST/SKIP on those SELECT statements, or convert them to derived tables with
ROWS clauses.
ROWS can also be used with the UPDATE and DELETE statements.
UNION
Available in: DSQL, ESQL, PSQL
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