На этот вопрос уже отвечали на этом форуме
Вот что пишут в ib71releasenotes.pdf
InterBase 6.5 introduces the following new keywords:
PERCENT, ROWS, TIES
• The ROWS clause
InterBase now supports a ROWS clause for SQL SELECT, UPDATE and DELETE statements. It has a general
syntax of ROWS <lower_value> [TO <upper_value>] [BY <step_value>] [PERCENT] [WITH TIES]. The ROWS
clause can be used in isolation or (most often) in conjunction with the SQL ORDER BY clause. The WITH TIES
clause must be used in conjunction with ORDER BY.
The ROWS clause introduces three new InterBase SQL keywords: ROWS, TIES, and PERCENT.
For more information, see the “Working with Data” chapter in the Embedded SQL Guide.