sql - vbnet select inside a select to a dt -

i got little code connect db, select data , write data file.

...

sqlquery = ("select field1 asl, field2 ncuen , field3 nfac , "" contr [2016cl]")  using connection sqlconnection = new sqlconnection("server=" & srvsql & ";database=" & bdsql & ";uid=" & usrsql & ";password=" & pswsql & ";")     connection.open()     using comm sqlcommand = new sqlcommand(sqlquery, connection)         dim rs sqldatareader = comm.executereader         dim dt datatable = new datatable         dt.load(rs)          call clcreatecsv.createcsvfile(dt, strfilenamediario)     end using     connection.close() end using 

.....

public shared sub createcsvfile(dt datatable, strfilepath string)     dim sw new streamwriter(strfilepath, false, encoding.utf8)     dim icolcount integer = dt.columns.count      each dr datarow in dt.rows         integer = 0 icolcount - 1             if not convert.isdbnull(dr(i))                 sw.write(dr(i).tostring())             end if             if < icolcount - 1                 sw.write(";")             end if         next         sw.write(sw.newline)     next     sw.close() end sub 

i need fill 4th value on select ("" contr) field table joins middle table.

field3 joins table on gfac.gfac2 table gfac joins 3rd table on ccli.ccli1 --> this 1 need on query

could use inner join but, afaik fields validate join.

how can this, writing all data [2016cl] , field contr each 1 of them if exists?

thanks in advance. if need more info, ask!

use left join instead inner join.

for example: select * table1 left join table2 on ...

that query selects rows table1. if row in table1 doesn't have match record in table2, table2 fields contains null.

hope helps.