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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
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.
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."
Download Oracle Database SQL Certified Associate (OCA) Exam Sample Questions PDF with Online Practice Test, Study Material and Exam Guide.
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 .
I want to make a SELECT that will return just the first row for each Val, ordering by Kind. Sample output: ID | Val | Kind ----- 2 | 1337 | 1 3 | 3 | 4 How can I build this query?
It says: "Contrary to popular belief COUNT(*) is faster than COUNT(1). If the rows are returned via an index, counting the indexed column - for example, COUNT(EMP_NO) is faster still. The optimizer realizes from the existence of the index that the column must also exist (non-null).
