sql server 2008 - How can I update a specific column in SQL from a backup database? -

i want copy values of single column backup current table.

this question seems asking same thing:

how update single column of table of data backup

i tried that, result subquery error:

msg 512, level 16, state 1, line 1
subquery returned more 1 value. not permitted when subquery follows =, !=, <, <= , >, >= or when subquery used expression.

here's statement i'm using:

update test.dbo.tbltag   set tagtypeid = (select tagtypeid testold.dbo.tbltag) 

do need different when using subquery in update statement?

update newdatabase.dbo.tablename set columnname=( select columnname olddatabse.dbo.tablename 'conditions' columnname=' ' ) columnname=' '