使用IF过滤数据

Question

students(studentID PK, A, B,sec..) FeesStructure(feeStruct PK, feeA, feeB, ..) FeesCollected(FeesID PK,studentID FK,feeStruct FK, A,B,..)

如果students.sec ='A'返回FeesStructure.feeA，FeesCollected.A ..等 必须创建一个基于if返回数据的视图。费用结构表有费用A，费用B. 仅根据学生的秒数申请。我需要根据students.sec

返回feeA或feeB

Answer 1

您可以使用CASE：

select students.studentID,
  case students.sec
    when 'A' then FeesStructure.feeA
    else FeesStructure.feeB
  end as feesStructure,
  case students.sec
    when 'A' then FeesCollected.A
    else FeesCollected.B
  end as feesCollected
from students, FeesStructure, FeesCollected
where students.studentID=FeesStructure.studentID
  and students.studentID=FeesCollected.studentID