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SELECT /*+ FIRST_ROWS */ field1, field2, field3, ... FROM table1, table2, table3, table4, table5 WHERE table1.id = table2.id AND table2.id = table3.id AND ... table5.userid = 1
20 Μαρ 2018 · FIRST_ROWS(n) is "optimize for the first n rows using all the normal costing algorithms", whereas FIRST_ROWS is "optimizer for the first rows using a pre-defined set of rules that will force index use, nested loops, etc."
Oracle SQL: Select first n rows / rows between n and m (TOP n/LIMIT queries) At times, it's necessary to select the first n rows or the rows between n and m (paging) from a table or query. Here are a few wrong and correct ways to do it.
For example, consider the following PL/SQL block that uses a cursor to retrieve the first 20 hits of a query and uses the FIRST_ROWS hint to optimize the response time:
21 Νοε 2012 · The hints FIRST_ROWS(n) (where n is any positive integer) or FIRST_ROWS instruct Oracle to optimize an individual SQL statement for fast response. FIRST_ROWS(n) affords greater precision, because it instructs Oracle to choose the plan that returns the first n rows most efficiently .
In the SELECT statement, specify the query in the WHERE clause with the CONTAINS operator. Also specify the SCORE operator to return the score of each hit in the hitlist. The following example shows how to enter a query: SELECT SCORE(1), title from news WHERE CONTAINS(text, 'oracle', 1) > 0;
The aggregate_function argument is any one of the MIN, MAX, SUM, AVG, COUNT, VARIANCE, or STDDEV functions. It operates on values from the rows that rank either FIRST or LAST . If only one row ranks as FIRST or LAST , then the aggregate operates on a singleton (nonaggregate) set.
