sql - Why is it that the IsEqual (=) operator is working faster than the IsNotEqual (<>) operator in Oracle? -

-

Like the title, if anyone has an answer then I want to know. I've been googling, but did not get a direct answer

Example:

This works 

  SELECT1 (*) to Table 1 TB1, Table 2 TB2 Where TB 1.Field 1 = TB 2.Table2

This may take time 

  SELECT COUNT (*) to Table 1 TB1, Table 2 TB2 Where TB1 Field 1 & lt; & Gt; It is important to realize that SQL is a declarative language and is not mandatory. One. You tell that in which situation you want to fit your data and not how those comparisons should be performed. This is the job of the database to find the fastest way to give you an answer (taken by a task). This means that your query appears that small changes can result in a wildly different query plan, which In turn, results in a wildly different runtime behavior.  
  =  Comparison can be changed, adapted and customized in the same way as easily joining the two areas. This means that general indices can be used to execute queries quickly, possibly reading actual data and instead using index only. 
 
 A  & lt; & Gt;  The second hand is completely calculated and checked for this condition, usually (it can be a method of optimizing with the correct index, but usually there is an index here Will not help) This will usually return a lot of results, which adds to the execution time.

Comments

Post a Comment

Popular posts from this blog

c# - sqlDecimal to decimal clr stored procedure Unable to cast object of type 'System.Data.SqlTypes.SqlDecimal' to type 'System.IConvertible' -

-
I'm new to this I'm writing a clr. stored procedure that can be used to get values ​​used in a calculation Call for another stored procedure for Gives an archived methodology int (I think SqlInt32? Value of the table's value is int) which is then necessary to convert to decimal. Here I have the code: Public static integral mood (SQL MDMMYLUE, escalistering AMY type, out of SQLDCM Result) {aResult = 0; Try {SqlConnection conn = New SqlConnection ("Reference Connection = True"); SqlCommand cmd = New SqlCommand ("sp_GetType", conn); Cmd.Parameters.AddWithValue ("@ myValueType", aMyValueType); Cmd.CommandType = CommandType.StoredProcedure; Conn.Open (); Object type = CMD. Exclamation Asser (); Conn.Close (); Decimal type FORCalculation = Convert. ToDecimal (type); Decimal value = convert toDecimal (aMyValue); // ** calculation calc = new calculation (); Decimal result = calorie.docalulation (typefarculation, value); I get an exception...
Read more

Calling GetGUIThreadInfo from Outlook VBA -

-
I need to find the active window'm writing a VBA macro in MS Outlook, which is a specific process. The goal of this is to get the active window / document name even if its original application has more than one document interface. User processor with GetCurrentThreadId is active, I am using GetGUIThreadInfo to get .dll. Here is the correct code: private type RECT as as Left LongPtr top LongPtr right LongPtr down LongPtr termination of private type GUITHREADINFO cbSize as LongPtr flags LongPtr hwndActive LongPtr hwndFocus LongPtr hwndCapture LongPtr as as as as as reset as LongPtr rcCaret as LongPtr hwndCreate as LongPtr hwndMoveSize as HwndMenuOwner end of Private Equity PtrSafe function GetWindowThreadProcessId Lib "user32" (_BVV hnw LongPtr as LongPtr Nig Mr. announced as PtrSafe function GetGUIThreadInfo Lib "user32" _ (ByVal dwthreadid as LongPtr, _ lpguithreadinfo as GUITHREADINFO) LongPtr Sub MyFunction () as dim strWindowTitle string = space as s...
Read more

Obfuscating Python code? -

-
I'm looking for a way to hide my Python source code. print "Hello World!" How can I encode this example so that it is not human-readable? I have been asked to use Base 64 but I'm not sure how. itemprop = "text"> It is limited only, first level ambiguous resolution, but has built-in: byte-code in Python Is a compiler for: dragon-o-m py_compile & lt; Your program.py & gt; creates a .pyo file with a byte-code, and where the docstrings are removed, etc. You can rename .pyo with the .py extension, and python & lt; Your program.py & gt; runs as your program, but it does not have your source code. PS : If your program blur modules like this, you need to rename them with the .pyc suffix (I Not sure it will not break a day), or you can work with .pyo and run them with python -o ... .pyo ( Import should work). This will allow dragon to search your modules (otherwise, Python looks for the .py module).
Read more