Aug 16, 2007
Hi,
I am facing a challenge and hope some one can help me with the query.
I have a school. School have classrooms. Classrooms are divided into various sections (Section A, Section B and so on) . Sections have subsections. Every student is allocated a rollnumber in that section.(Subsection is just for dividng the sections. it has no other use.) Now the student is given a choice to specify his own roll( DesiredRoll) in that section. If two children select the same rollno, then the system internally allocates a trackingno.(There can be multiple roll no as these are allocated manually by admin). Let me demonstrate this:
So when the first entry is made in the db, and let us say that the section to be allocated is A, RollNo is 1 and the DesiredRoll is 1
Student 1 Section A Subsection 1 Roll No 1 DesiredRoll 1 TrackingNo 0
The second entry is made in the db and let us say the section to be allocated is A, RollNo is 2 and the DesiredRoll is 2
Student 2 Section A Subsection 1 Roll No 2 DesiredRoll 2 TrackingNo 0
Now let us say there is a 3rd entry the section to be allocated is A, RollNo is 3 but the DesiredRoll is 1. Now since the DesiredRoll has already been taken, we will allocate the DesiredRoll 1, however now the trackingNo will be 1
Let us say there is a 4th entry is made, the section to be allocated is A, RollNo is 4 but the DesiredRoll is again 1. Now since the DesiredRoll has already been taken, we will allocate the DesiredRoll 1, however now the trackingNo will be 2
Similarly this logic will work for different sections. How will I write a query so that I can detect this scenario and increment the tracking no or allocate a tracking no of 0 if there is a new entry made in that section
The structure of the table is as follows:
IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[Student]') AND type in (N'U'))
BEGIN
CREATE TABLE [dbo].[Student](
[RID] [int] NOT NULL,
[Class] [int] NULL,
[Section] [char](1) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[SubSection] [int] NULL,
[RollNo] [int] NULL,
[DesiredRoll] [int] NULL,
[TrackingNo] [int] NULL
)
END
GO
INSERT [dbo].[Student] ([RID], [Class], [Section], [SubSection], [RollNo], [DesiredRoll], [TrackingNo]) VALUES (1, 1, N'A', 1, 1, 1, 0)
INSERT [dbo].[Student] ([RID], [Class], [Section], [SubSection], [RollNo], [DesiredRoll], [TrackingNo]) VALUES (2, 1, N'A', 1, 2, 2, 0)
INSERT [dbo].[Student] ([RID], [Class], [Section], [SubSection], [RollNo], [DesiredRoll], [TrackingNo]) VALUES (3, 1, N'A', 1, 3, 1, 1)
INSERT [dbo].[Student] ([RID], [Class], [Section], [SubSection], [RollNo], [DesiredRoll], [TrackingNo]) VALUES (4, 1, N'A', 1, 4, 1, 2)
INSERT [dbo].[Student] ([RID], [Class], [Section], [SubSection], [RollNo], [DesiredRoll], [TrackingNo]) VALUES (5, 1, N'A', 12, 3, 0, 0)
INSERT [dbo].[Student] ([RID], [Class], [Section], [SubSection], [RollNo], [DesiredRoll], [TrackingNo]) VALUES (6, 1, N'A', 12, 4, 0, 0)
INSERT [dbo].[Student] ([RID], [Class], [Section], [SubSection], [RollNo], [DesiredRoll], [TrackingNo]) VALUES (7, 1, N'B', 5, 1, 0, 0)
INSERT [dbo].[Student] ([RID], [Class], [Section], [SubSection], [RollNo], [DesiredRoll], [TrackingNo]) VALUES (8, 1, N'B', 5, 2, 0, 0)
INSERT [dbo].[Student] ([RID], [Class], [Section], [SubSection], [RollNo], [DesiredRoll], [TrackingNo]) VALUES (9, 1, N'B', 5, 3, 0, 0)
INSERT [dbo].[Student] ([RID], [Class], [Section], [SubSection], [RollNo], [DesiredRoll], [TrackingNo]) VALUES (10, 1, N'B', 10, 1, 0, 0)
INSERT [dbo].[Student] ([RID], [Class], [Section], [SubSection], [RollNo], [DesiredRoll], [TrackingNo]) VALUES (11, 1, N'B', 10, 2, 0, 0)
INSERT [dbo].[Student] ([RID], [Class], [Section], [SubSection], [RollNo], [DesiredRoll], [TrackingNo]) VALUES (12, 1, N'B', 10, 3, 0, 0)
INSERT [dbo].[Student] ([RID], [Class], [Section], [SubSection], [RollNo], [DesiredRoll], [TrackingNo]) VALUES (13, 1, N'B', 11, 1, 0, 0)
INSERT [dbo].[Student] ([RID], [Class], [Section], [SubSection], [RollNo], [DesiredRoll], [TrackingNo]) VALUES (14, 1, N'B', 11, 2, 0, 0)
INSERT [dbo].[Student] ([RID], [Class], [Section], [SubSection], [RollNo], [DesiredRoll], [TrackingNo]) VALUES (15, 1, N'B', 11, 3, 0, 0)
Thanks
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