mysql - What are the known ways to store a tree structure in a relational DB? -

-

There, that means each record points to their parents.
Maintain that hard to read but easy to maintain.

And then there is a "directory structure key" method: 

  0001.0000.0000.0000 main branch 1 0001.0001.0000.0000 one of the main branch etc etc

Super easy to read, but difficult to maintain.
What are the other ways and their cons / professional?

As always: There is no best solution. Each solution makes different things easy or difficult. The right solution for this depends on which action you will take.

Relative approach with Parent-ID:

Professionals:

    Easy to implement

  • Easy to move any other parent to a large sub-location

  • Insert is cheap

  • Accessible area directly in SQL

Cons:

  • Retrieving the entire tree is recurring And so expensive

  • All parents are too expensive to find (SQA Revised ...)

Modified Prior Tree Treversal (A Start and End Point Saving):

Professionals:

  • Retrieving the entire tree is easy and cheap

  • It is cheaper to find all parents

  • Fields reaching directly in SQL

    >

  • Bonus: You are also saving the order of the hair node within your original node

Cons:

  • Insert / update is too expensive Because you have to update many nodes

Save paths in each node:

Professionals:

  • Insert is cheap

Cons:

  • Running a complete tree is expensive

  • The path on the way you save , You will not be able to work with it directly in SQL, so you will always need to get & amp; If you want to change it, then parse it.

I like one of the last two, depending on how often the data changes.

Also see:


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