c# - (db) Add another syntax in WHERE/SET(UPDATE) part? -


overview: code student can sign courses want read. he should accepted 1 course, not more(this got problem with). although student can search 3 courses @ same time priority selection 1-3.

if courses full students queue-index, starting 1 , up. once there's free spot in course(that's syntax below being used, looping each free spot in course), student queue-index 1 hit 0 , he's accepted course. 

  cmd.commandtext = "update [register]                        set queueindex = queueindex - 1,                        accepted = iif(queueindex = 1, 1, 0)                        queueindex > 0 , courseid = @cid;";

however don't know how improve syntax , implement checker in syntax if student accepted in other courses. if is, should not accepted(and set queue-index 0 he's no longer in queue, , accepted still false) , check next student instead. don't know how improve syntax.

in db-table, i'm using courseid, studentid, accepted(bool), selection(for 1-3 course choices, not important here), queueindex(int)

i implement kind of.. if current student queueindex = 1, , if of his/studentid choices/selections accepted = true queueindex = 0 , set accepted = false, current choice no longer relevant since he's accepted.

or and (if (studentid queueindex= 1 have (accepted=true) in choices/courseid)) = false in where? syntax in part or something.

edit: thinking in where-part

and 0 = (select count(accepted) [register] studentid = (select studentid [register] queueindex = 1 , courseid = @cid)) , accepted = true

edit2: ctumturk made me realize asked wrong question. should set student queueindex = 0 course she/he selected once accepted.


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