Copying non duplicated data

[bill robson]

Hi. I am stuck and was hoping for some help. I am using MSSQL and I need to extract data from one field (A) and append it to a second field (B) but only if the data in (A) does not allready exists in (B). The querry is run many times so the (B) field should only grow when something new is added to (A).
EX.
Field (A) = 123
Field (B) = ""
After first sql command
Field (A) = 123
Field (B) = 123

Field (A) gets changed to
123
456
After second sql command
Filed (B) should be
123
456

not
123
123
456

Any ideas are appreciated - Thanks

[ronverdonk]

I will not ask if field B is in the same row as field A because then you would not need this operation, so I assume that B is in another table.
Since B is an exact copy of A, why don't you just replace the entire column B with column A with an UPDATE tableB... SET B=(SELECT A from tableA) ... ?
Or is this not what you meant?

Ronald :cool: