mysql - 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 View 。 Fees结构表有feeA、feeB仅根据学生的秒数适用。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