Shell Programming and Scripting

# grep -o 'DB.*[^ ;]'  file
DB.Employee
DB_T.Emp
DB.Test
DB.Dept
DB_T.Ter
#

# grep 'DB' file | sed  's/.*\(DB.*[^ ;]\);*/\1/'
DB.Employee
DB_T.Emp
DB.Test
DB.Dept
DB_T.Ter
#

# fomatted for easier reading; comments completely unnecessary....
# cannonicalise each word in <> branch to keep if matched
# if not matched; delete record; loop to next record
# delete all chrs upto first <
# delete all characters between > <  (multiple matches on same record)
# delete leading <
# delete trailing > and any trailing whitespace
# replace remaining > with newline (separate multiple to one per output record)

sed 's/DB[._][^ \t]*/<&>/g; t keep
d 
: keep
{
        s/[^<]*//;
        s/> [^<]*/> /g;
        s/<//g;
        s/>[ \t]*$//;
        s/> */\n/g; 
}' <file

Input:
Replace DB.Employee  DBxNOTme
as 
select 
column1
column2
from DB_T.Emp bar DB_T.foo DB.goo
and DB_Testx
DB.Testy      and more text
DB.Testz and    more text and DB.Testa
and 
DB.Depta
and
DB_T.Ter;

Output:                          
DB.Employee
DB_T.Emp
DB_T.foo
DB.goo
DB_Testx
DB.Testy
DB.Testz
DB.Testa
DB.Depta
DB_T.Ter;

tr -s "[ \t]" "\n" <file | grep 'DB[._].*'