how to determine the first column with null value

  • Hello

    I have a table with 7 columns like Cumulative_cnt, AX1, AX2, AX3, AX4, AX5, POS

    i want to find the first AX column with a 'null' and assign that column number to POS as a value

    for e.g. if AX3 has the first null value then POS is assigned a value 3.

    table is as follows

    AX1-AX5 are varchar

    all columns after the first column with a Null is Null

    all columns preceding the first column with Null has a value

    at least one column has a value and is not null which is usually AX1

  • MadRazzi (2/22/2013)


    Hello

    I have a table with 7 columns like Cumulative_cnt, AX1, AX2, AX3, AX4, AX5, POS

    i want to find the first AX column with a 'null' and assign that column number to POS as a value

    for e.g. if AX3 has the first null value then POS is assigned a value 3.

    table is as follows

    AX1-AX5 are varchar

    all columns after the first column with a Null is Null

    all columns preceding the first column with Null has a value

    at least one column has a value and is not null which is usually AX1

    This screams of poor design but the query is pretty simple.

    Update YourTable

    set POS =

    case

    when AX1 is not null then 1

    when AX2 is not null then 2

    when AX3 is not null then 3

    when AX4 is not null then 4

    when AX5 is not null then 5

    end

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  • what if ax2 through ax5 is null for a record

    wouldn't the case statement assign value 5 to POS?

  • MadRazzi (2/22/2013)


    what if ax2 through ax5 is null for a record

    wouldn't the case statement assign value 5 to POS?

    no.

    the case statement stops executing as soon as a match is found in the criteria is met.

    other items are not evaluated. and they are evaluated in the order you put in the order that the case statement is created.

    so it would return 2 in your example where 2-5 are null.

    Lowell


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