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Thread: Need help with a query

  1. #1
    Join Date
    Sep 2010
    Posts
    1

    Need help with a query

    I have 2 table
    first table. employee( empid- primary key ,empname)
    eg: employee table
    1 john
    2 martyn
    3 davis

    second table documents(empid,documentname)
    eg :
    1 address.doc
    1 worksheet.doc
    1 salaryslip.doc
    3 address.doc


    each employee have only one entry in employee table
    but in document table , zero or more entries are inserted for each employee.

    i want to write a query that gives an output shown in below

    empid empname documentflag
    1 john true
    2 martyn null
    3 davis true

    that is, if documents table have at least one entry for an employee ,then set corresponding document flag is true. otherwise set document value as null

  2. #2
    Join Date
    Feb 2011
    Posts
    7
    select a.empid,a.empname,count(b.empid) from employee a,documents b
    where a.empid=b.empid group by a.empid,a.empname,b.empid

  3. #3
    Join Date
    Feb 2011
    Posts
    6
    Try this:
    select e.name, if(count(d.document_name)>0,'True','False') as flag from employee e left join document d on e.name = d.employee group by e.name;

    Bert

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