Off topic:Help with awk statement in a shell script

Question

[terry.walters]

I have a file that contains the following line that is the input to a SYBASE query. where so.name = "tablename" I run this query in a shell script within a for loop. I am attempting to get all the column names in each table in a SYBASE ASE database. My for loop is something like this

 for tablename in `cat $TBLNAME.$DBNAM.out
do
  awk '$1=="where"{$4="\"$tablename\""}1' $CLMNSQL . tmp2 && mv tmp2 $CLMNSQL 
  get_column_names
done

the data in $TBLNAME.$DBNAM.out looks something like this

tbaccessfilter
 tbbillingrules
 tbconcurrentusers
 tbconfigaudit
 tbconfigname
 tbconfiguration
 tbcustomer
 tbcustomersdomtype
 tbcustomersshippingtype

My question is how do I relpace the "tablename" in the file $CLMNSQL with what is contained in the $tablename variable in my awk statement, because what I have there does not work? What would the sed command look like if i use sed instead?