Aggregate Single-row In/Exists Not in/Not exists in Java

Generation Code 3/9 in Java Aggregate Single-row In/Exists Not in/Not exists

Aggregate Single-row In/Exists Not in/Not exists
ANSI/AIM Code 39 Generator In Java
Using Barcode encoder for Java Control to generate, create Code 3/9 image in Java applications.
www.OnBarcode.com
Code 3 Of 9 Recognizer In Java
Using Barcode reader for Java Control to read, scan read, scan image in Java applications.
www.OnBarcode.com
You will note, of course, that a single subquery can easily fall across several of these categories there is nothing stopping a correlated subquery from being an aggregate, returning at most one row for a nonexistence test. (But at least, when I see one like that, I know that I may have to think about it very carefully if it s not doing what I expect.) In this volume, I m going to stick to simple subqueries, play about a little bit with in/exists, not in/not exists, and say a little bit about unnesting, semi-joins, and anti-joins. So let s go back to script filter_cost_01.sql, which started this chapter, and modify it to allow 9i to do what it wants with our very first test case. What does the execution plan look like See script unnest_cost_01.sql in the online code suite. Execution Plan (9.2.0.6 with no hints - an unnest occurs) ---------------------------------------------------------0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=100 Card=1000 Bytes=98000) 1 0 HASH JOIN (Cost=100 Card=1000 Bytes=98000) 2 1 VIEW OF 'VW_SQ_1' (Cost=64 Card=6 Bytes=156) 3 2 SORT (GROUP BY) (Cost=64 Card=6 Bytes=48) 4 3 TABLE ACCESS (FULL) OF 'EMP' (Cost=35 Card=20000 Bytes=160000) 5 1 TABLE ACCESS (FULL) OF 'EMP' (Cost=35 Card=20000 Bytes=1440000) Execution Plan (9.2.0.6 when we forced a FILTER) ---------------------------------------------------------0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=35035 Card=1000 Bytes=72000) 1 0 FILTER 2 1 TABLE ACCESS (FULL) OF 'EMP' (Cost=35 Card=1000 Bytes=72000) 3 1 SORT (AGGREGATE) 4 3 TABLE ACCESS (FULL) OF 'EMP' (Cost=35 Card=3333 Bytes=26664)
Creating EAN13 In Java
Using Barcode generator for Java Control to generate, create GTIN - 13 image in Java applications.
www.OnBarcode.com
Make PDF 417 In Java
Using Barcode generator for Java Control to generate, create PDF 417 image in Java applications.
www.OnBarcode.com
CHAPTER 9 QUERY TRANSFORMATION
Making Code 128A In Java
Using Barcode creation for Java Control to generate, create Code 128 Code Set B image in Java applications.
www.OnBarcode.com
Make QR Code In Java
Using Barcode creator for Java Control to generate, create QR Code JIS X 0510 image in Java applications.
www.OnBarcode.com
The optimizer has taken our original query and rewritten it to avoid the filter. In effect, the optimizer has executed the following statement (the no_merge hint is there just to make sure that Oracle doesn t decide to use some trick of complex view merging to expand the query, and do something completely different with it): select /*+ ordered use_hash(outer) */ outer.* from ( select /*+ no_merge */ dept_no, avg(inner.sal) emp inner dept_no ) inner, emp outer where and ; outer.dept_no = inner.dept_no outer.sal > inner.avg_sal
GTIN - 128 Generation In Java
Using Barcode printer for Java Control to generate, create EAN128 image in Java applications.
www.OnBarcode.com
British Royal Mail 4-State Customer Barcode Drawer In Java
Using Barcode generation for Java Control to generate, create British Royal Mail 4-State Customer Barcode image in Java applications.
www.OnBarcode.com
avg_sal
Code 3/9 Maker In None
Using Barcode maker for Excel Control to generate, create USS Code 39 image in Microsoft Excel applications.
www.OnBarcode.com
Code 39 Full ASCII Creation In Java
Using Barcode creation for Java Control to generate, create ANSI/AIM Code 39 image in Java applications.
www.OnBarcode.com
from group by
UPC-A Drawer In Objective-C
Using Barcode creator for iPad Control to generate, create UPCA image in iPad applications.
www.OnBarcode.com
Making PDF417 In C#
Using Barcode generation for .NET Control to generate, create PDF417 image in .NET framework applications.
www.OnBarcode.com
Note the appearance of the line view of vw_sq_1 in the execution plan. This is an indication that the optimizer has done some query unnesting. Alternative names for views you can get as a result of unnesting are vw_nsq_1 and vw_nso_1 (with a change in the numeric bit for complicated SQL that manages to produce more than one unnesting action). Those of you who have read Oracle Performance Tuning 101 by Gaja Vaidyanatha et al. (Osborne McGraw-Hill, 2001) will recall at this point that one of the authors suggestions for dealing with certain types of subquery was to convert the subquery into an inline view and put it into the body of the query. This was such a good idea that the optimizer now does it automatically. It happens more or less inevitably in 9i, but is a cost-based decision in 10g. The test case produces exactly the same final plan for 10g as it does for 9i, including the cardinality of 1,000 rather than the 167 that 10g produced when doing a filter (so the cardinality is still wrong with its bind variable 5%, but it is closer). However, when you look at the 10053 trace, you find that 9i has produced just two general plans sections, whereas 10g has produced ten sections before producing a final course of action, suggesting that the decision to unnest was driven by the cost. The first section in the 9i trace generated the strategy for instantiating the inline aggregate view, and the second section worked out how to join the aggregate view to the other table. The trace file for 10g started with the same two sections, and then seemed to have a section calculating the effect of joining the two tables before doing an aggregation (which I thought should have been blocked by the no_merge hint), followed by various repetitions of very similar calculations. Lurking within the later calculations were two sections relating to costing the query using the old 8i filter option which was more expensive than the unnesting option, and therefore ignored (although in a secondary experiment, I changed the data so that the filter was cheaper than the unnest, and the filter was chosen automatically).
Make Denso QR Bar Code In VS .NET
Using Barcode generation for .NET framework Control to generate, create QR-Code image in .NET applications.
www.OnBarcode.com
Reading Code-39 In C#
Using Barcode reader for VS .NET Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
EAN 13 Scanner In VS .NET
Using Barcode scanner for .NET Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
Read UPC Code In .NET
Using Barcode decoder for VS .NET Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
Barcode Scanner In Java
Using Barcode Control SDK for Java Control to generate, create, read, scan barcode image in Java applications.
www.OnBarcode.com
PDF417 Decoder In Java
Using Barcode recognizer for Java Control to read, scan read, scan image in Java applications.
www.OnBarcode.com
Decoding Code 128C In C#
Using Barcode reader for VS .NET Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
EAN / UCC - 13 Creation In Visual Basic .NET
Using Barcode maker for .NET Control to generate, create GS1 - 13 image in VS .NET applications.
www.OnBarcode.com
Copyright © OnBarcode.com . All rights reserved.