What is the difference between Count (*) and Count (1)?

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• What is the difference between count (1) selection of the tab and select count (*) tab;

  What is the difference between count (1) selection of the tab and select count (*) tab;

  994122 wrote:

  Hello

  SQL > set timing on

  SQL > select count (*) of the emp

  2 where deptno = 30;

  COUNT (*)

  ---------------

  6

  Elapsed time: 00:00:00.01

  SQL > select count (1) of the emp

  2 * where deptno = 30

  SQL > /.

  COUNT (1)

  -------------

  6

  Elapsed time: 00:00:00.01

  See that both give the same time

  Do you really think the 100th's of a second it takes 6 rows from counting will truly representative of the difference it takes actually?

  Such a small data set cannot possibly show no difference to these larger units of time (in the calculation of terms where we have millions of instructions per second in lieu)

  As the link to the FAQ provided in the response of Anton (first response on this thread) Watch, count (1) and count (*) are essentially the same, except that count (1) actually get re-written by the query re - write the step of the optimization to make it count (*).

  Generally 'count (*)' makes more sense language, because it reads like "count" while "count (1)" reads as "count we ', which does not have as much good sense when you actually count all.

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  I'm sorry if here is not the right place for this post.

  What is the difference between extensions and Plugins and Add-ons? Apparantely, they differ in some sense or aspect, but I do not know how. Please, if it is not too complicated, explain in detail and simple language. Thanks in advance to 1 million.

  Kind regards
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  I wonder what are the differences between AXIEM and EMSight. Are associated with application? One is better than the other? Please explain.

  AWR estimated AXIEM most powerful plan EM Simulator around.   AXIEM is at the center of continuous research and improvement, while EMSight is only worked on if revealed serious flaws.  Here is a summary of the differences:

  Mesh

  • EMSight must mesh the nearest grid drivers using rectangles.  This causes the mesh to have more elements mesh when there are small and large geometries.  The grid should be small enough to capture the small geometry but then causes large geometries to mesh more.   In addition, angled or curved structures causes inefficiencies mesh.
  
  
  • AXIEM STS forms, rather than a grid.  In addition, the mesh can be rectangle or triangle.   This allows a much more efficient mesh.   AXIEM generally have a much more efficient
  
  
  • AXIEM contains the ability to process forms to clean geometries that cause inefficiencies of the mesh.  EMSight does not have this feature.
  
  
  • AXIEM can forms thick metal mesh, EMSight can not, and user must make approximations when thick metal will change coupling (loss is recorded properly with the thickness of the metal)

  Ports

  • The ports are for the most part similar, but parasites due on AXIEM ports are less.  In addition, the AXIEM has a side wall, thus the effects of not move of the terms of reference of the edge of the line are a lot less AXIEM in.
  
  
  • Ports can be added to most any place in geometry with AXIEM.  For EMSight, the ports are usually only added outside the geometry and have limitations to the aircraft on either side of the reference speaker.

  Problem solvers

  • EMSight does not have a low frequency Solver.  Stop low-frequency and then extrapolate to DC.  This usually works well, but you must take into account if the extrapolation is accurate.  AXIEM presents both a low and high frequency Solver so will do better in a low frequencies generally much better in DC.
  
  
  • Solver of EMSight scales O (n) ^ 2 for memory and O (n) ^ 3 for the moment.   It has a special algorithm to break the question of memory, but the question of time is the killer.  AXIEM has a direct Solver which scales in the same way and an iterative Solver which will scale O (nlogn).   In other words, AXIEM can solve a lot of bigger problems than EMSight.
  
  
  • Several AXIEM processes are multithreaded as EMSight.

  Speaker

  • EMSight is inside a perfect driver side wall.   This works well if you the circuit is in the same cavity.  If not, you must know the rules of them on to the forms of space of the flanks and how that much to extend the port could reference planes.   AXIEM is not here.   AXIEM does not currently have to simulate a perfect driver side wall.

  I don't know that I missed a few aspects of the tools.   From the point of view of the AWR that AXIEM is the tool of choice, except in a few cases have been EMSight may be required.

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  Hi SirNickLong,
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  Sometimes the only way to upgrade is to do a clean install,

  " Upgrade Windows XP to Windows 7 "

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  "Upgrading from Windows Vista to Windows 7"

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