KSH-update : Get rows affected - sql

Question

Hello I'm querying a teradata database like that :
for var in `db2 -x "$other_query"`;
do
query_update_date="update test SET date =Null WHERE
name_test='$var '"
db2 -v "$query_update_date"
done
My query is executed but what I would like to print the query_update_date only when one row or more is affected (changed ) by update.
Example :
If I have
First query of loop :
query_update_date="update test SET date =Null WHERE
name_test='John'"
and second query of the loop :
query_update_date="update test SET date =Null WHERE
name_test='Jeff'"
and in my table before the query :
name_test date
Jeff 01/07/2016
John Null
After the query
name_test date
Jeff Null
John Null
The date from John was already null , so it hasn't been affected by update.
And
db2 -v "$query_update_date"
print my queries. What I want for previous example is to print in my logs only
query_update_date="update test SET date =Null WHERE
name_test='Jeff'"

Answer 1

Take snapshots of the table before and after you execute the query. Use whatever tools you like: how about (assuming SQL) SPOOL a "SELECT * FROM T" query into this file beforehand, and into that file afterwards. Use the UNIX diff command to compare the two files, and merely count the length of its output:
LINES_OUT=$(diff oldResults newResults | wc -l)
if [[ $LINES_OUT = 0 ]]
then
# log the query, however you do that
fi
If $IS_ANY_DIFF is true, log the query; otherwise, don't.