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  4. Single Update Query for.....

Single Update Query for.....

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  • S Sanjay K Gupta

    create table trns.a(id int,name varchar(20))
    insert into TRNS.a values(1,'A')
    insert into TRNS.a values(2,'B')
    insert into TRNS.a values(3,'C')
    insert into TRNS.a values(4,'D')
    insert into TRNS.a values(5,'E')
    insert into TRNS.a values(6,'F')

    select *from a
    if you run select Query, you will get
    id name

    1 A
    2 B
    3 C
    4 D
    . .
    . .

    Q. I need to Update the above table in single update statement to get result like
    select *from a

    id name

    1 B
    2 A
    3 D
    4 C
    . .
    . .

    Note: I know the solution, So I have put this question under "Clever Code".

    A Offline
    A Offline
    Al_Brown
    wrote on last edited by
    #7

    Slight modification of Luc's idea:

    UPDATE a INNER JOIN a AS a2 ON a.id = 1+((a2.id-1)^1) SET a.name = a2.name

    S 1 Reply Last reply
    0
    • A Al_Brown

      Slight modification of Luc's idea:

      UPDATE a INNER JOIN a AS a2 ON a.id = 1+((a2.id-1)^1) SET a.name = a2.name

      S Offline
      S Offline
      Sanjay K Gupta
      wrote on last edited by
      #8

      No, your query is giving error.. Incorrect syntax near the keyword 'INNER'.

      A 1 Reply Last reply
      0
      • S Sanjay K Gupta

        No, your query is giving error.. Incorrect syntax near the keyword 'INNER'.

        A Offline
        A Offline
        Al_Brown
        wrote on last edited by
        #9

        Which database system are you using? Try it without the word INNER.

        S 1 Reply Last reply
        0
        • A Al_Brown

          Which database system are you using? Try it without the word INNER.

          S Offline
          S Offline
          Sanjay K Gupta
          wrote on last edited by
          #10

          SQL Server 2008

          A 1 Reply Last reply
          0
          • S Sanjay K Gupta

            SQL Server 2008

            A Offline
            A Offline
            Al_Brown
            wrote on last edited by
            #11

            Ah, OK. In that case use:

            UPDATE a SET a.name = a2.name FROM a INNER JOIN a AS a2 ON a.id = 1+((a2.id-1)^1)

            S 1 Reply Last reply
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            • A Al_Brown

              Ah, OK. In that case use:

              UPDATE a SET a.name = a2.name FROM a INNER JOIN a AS a2 ON a.id = 1+((a2.id-1)^1)

              S Offline
              S Offline
              Sanjay K Gupta
              wrote on last edited by
              #12

              Clever Code!! That is what I was for looking for. Thanks. .. But here is id in sequence. Consider the condition when Id column is not present then how could you update Odd row to Next Even Row and Even Row to Previous Odd Row.

              A 1 Reply Last reply
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              • S Sanjay K Gupta

                Clever Code!! That is what I was for looking for. Thanks. .. But here is id in sequence. Consider the condition when Id column is not present then how could you update Odd row to Next Even Row and Even Row to Previous Odd Row.

                A Offline
                A Offline
                Al_Brown
                wrote on last edited by
                #13

                This is just theoretical, right....? You could do something like this:

                UPDATE a SET name = (SELECT TOP 1 a2.name FROM a AS a2
                WHERE a2.id * ((a.id & 1) * 2 - 1) > a.id * ((a.id & 1) * 2 - 1)
                AND (a2.id ^ a.id) & 1 = 1
                ORDER BY a2.id * ((a.id & 1) * 2 - 1))

                But then you're going into Hall Of Shame territory

                1 Reply Last reply
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                • S Sanjay K Gupta

                  create table trns.a(id int,name varchar(20))
                  insert into TRNS.a values(1,'A')
                  insert into TRNS.a values(2,'B')
                  insert into TRNS.a values(3,'C')
                  insert into TRNS.a values(4,'D')
                  insert into TRNS.a values(5,'E')
                  insert into TRNS.a values(6,'F')

                  select *from a
                  if you run select Query, you will get
                  id name

                  1 A
                  2 B
                  3 C
                  4 D
                  . .
                  . .

                  Q. I need to Update the above table in single update statement to get result like
                  select *from a

                  id name

                  1 B
                  2 A
                  3 D
                  4 C
                  . .
                  . .

                  Note: I know the solution, So I have put this question under "Clever Code".

                  P Offline
                  P Offline
                  PIEBALDconsult
                  wrote on last edited by
                  #14

                  You could have made this a Friday Programming Quiz. UPDATE a SET id = CASE WHEN id/2.0=CAST(id/2.0 AS INTEGER) THEN id-1 ELSE id+1 END

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                  0
                  • S Sanjay K Gupta

                    You have updated the Id. What would you do if there may some more columns like Address and Mobile.... Only Update Name column. The result should be.... Id Address Name --------------------------------------- 1 Address1 B 2 Address2 A 3 Address3 D 4 Address4 C . .... . . .... .

                    P Offline
                    P Offline
                    PIEBALDconsult
                    wrote on last edited by
                    #15

                    That was not part of the specification.

                    1 Reply Last reply
                    0
                    • L Luc Pattyn

                      UPDATE trns.a SET id=1+((id-1)^1)

                      :)

                      Luc Pattyn [My Articles] Nil Volentibus Arduum

                      I Offline
                      I Offline
                      ian dennis 0
                      wrote on last edited by
                      #16

                      Surely anything to the power of 1 is itself? so (id-1)^1 = id-1

                      L 1 Reply Last reply
                      0
                      • I ian dennis 0

                        Surely anything to the power of 1 is itself? so (id-1)^1 = id-1

                        L Offline
                        L Offline
                        Luc Pattyn
                        wrote on last edited by
                        #17

                        ian dennis wrote:

                        anything to the power of 1 is itself

                        yes

                        ian dennis wrote:

                        so (id-1)^1 = id-1

                        no, that is simply never true in the programming languages I use. Including SQL. :)

                        Luc Pattyn [My Articles] Nil Volentibus Arduum


                        Fed up by FireFox memory leaks I switched to Opera and now CP doesn't perform its paste magic, so links will not be offered. Sorry.

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