database - Converting a schema to a second normal form -

-

consider basic table schema:

studentid, student name, department, coursecode, course name, year-semester, grade

how can convert the second normal form identifying functional dependencies?

i use mnemonic device first 3 normal form. use word repeat ignoring vowels. first no repeating groups or multivalued fields, second no partial dependence on primary key , no transitory dependence.

in case looks 1nf problem rather 2nf. 2nf means partial dependence , looking @ table there no composite primary key i.e primary keys having more 1 field therefore there no possibility of partial dependence. 1nf there 2 possibilities 1 has repeated groups other 1 multi- valued fields. so, example of 1nf repeating groups here

and multi-valued example here

it better if have actual records/rows of table , ask question: there repeating groups or there multivalued fields? there can begin answering problem using examples provided above.

by way here in (stackoverflow) no-no come question without doing effort in part. have beeen if come answer first before you. understand 1st time posting here , forgivable @ least here.

based on new information:

you have:

 table : student  fields : studentid, student name, department   table : course  fields : coursecode, course name, year, semester   table: tablegrade  fields : studentid, courseid, grade

and if follow want tablegrade no course taken (or course offered see later on)then need either add 1 more field in course table match tablegrade table or change 1 field of tablegrade:

if want change course table this:

table: course fields: courseid, coursecode, course name, year, semester

if want change tablegrade this:

table: tablegrade fields: studentid, coursecode, grade

however, if @ course table there problem. let's have original one:

coursecode, course name, year, semester

if @ course name come on repeating unnecessarily violation 1nf, is, no repeating groups. in case coursecode , course name repeats unnecessarily.

and if use observe proposed changes mentioned still have problem:

courseid, coursecode, course name, year, semester

in case violates 3nf says no transient dependence. in case course name dependent on coursecode , not on courseid primary key.

another thing know courses has sections, have @ least

 coursecode, course name, section, year, semester

so, that's why make more sense have courses taken or more appropriately course offered , add table name courses reference table.

so, new schema like:

 table : student  fields : studentid, student name, department   table : coursesoffered  fields : courseid, coursecode, section, year, semester   table: courses  fields : coursecode, course name   table: tablegrade  fields : studentid, courseid, grade

do 1 makes sense you?


Popular posts from this blog

How to calculate SNR of signals in MATLAB? -

-
i've encountered simple, yet fundamental problem on calculating snr: there several signals : s1 = original , pure clean signal without noise. n1 = white gaussian noise going added s1. s2 = s1 + n1 (the noisy signal before performing noise-reduction algorithm) s3 = noise-reduced signal (after performing noise reduction algorithm) n2 = s3 - s1 (the amount of noise after performing noise-reduction algorithm) now want compare snr before , after performing noise-reduction algorithm. which signals should consider snr_before!? s1/n1 or s2/n1 ? which signals should consider snr_after!? s3/n1 or s3/n2 ? which commands or functions should use in matlab in order compute snr_before , snr_after? thanks billion putting time on helping me. what know calculating snr before : snrbeforenoise = mean( signal .^ 2 ) / mean( noise .^ 2 ); and snr after : residual_noise = signal - noise_reduced_signal; snr_after = mean( signal .^ 2 ) / mean( residual_noise .^ 2...
Read more

c# - Attempting to upload to FTP: System.Net.WebException: System error -

-
i have api takes in xml , uploads files based on information in xml. uploads on schedule (also xml), , have tested surrounding , know works. i getting error 40% of time on first file attempt upload in each time cycle (time cycle = 45 minutes files, 30 minutes others). here code upload: try { loggerftp.log("uploading file: " + filename, false); // create request. ftpwebrequest request = (ftpwebrequest)webrequest.create(appsettingsftp.ftpurl + @"/" + filename); request.method = webrequestmethods.ftp.uploadfile; request.timeout = 6000000; //set 100 minutes //request.timeout = -1; //set infinite // add login credentials. request.credentials = new networkcredential(appsettingsftp.ftplogin, appsettingsftp.ftppassword); // grab file contents. streamreader sourcestream = new streamreader(appsettingsftp.uploadfiledirectory + filename); byte[] filecontents = encoding.utf8.getbytes(sourcestream.readtoend()); sourcest...
Read more

ios - UISlider customization: how to properly add shadow to custom knob image -

-
Image
i need place custom knob image shadow uislider. far have image of 38x38, of there region defines shadow of knob. now while using image, when slide knob extreme ends actual knob not able cover end points, hence end points visible under transparent region of knob image this code using customize uislider uiimage *slidebtimg = [uiimage imagenamed:sliderknobimg]; [self.ratingslider setthumbimage:slidebtimg forstate:uicontrolstatenormal]; [self.ratingslider setthumbimage:slidebtimg forstate:uicontrolstatehighlighted]; how can implement custom knob shadow beneath it, covering end points?? look inside uislider.h , there methods let customize slider knob , track needed. (ios 2.0 , above) // lets subclass lay out track , thumb needed - (cgrect)minimumvalueimagerectforbounds:(cgrect)bounds; - (cgrect)maximumvalueimagerectforbounds:(cgrect)bounds; - (cgrect)trackrectforbounds:(cgrect)bounds; - (cgrect)thumbrectforbounds:(cgrect)bounds trackrect:(cgrect)rect value:...
Read more