Unix Script exiting when select query returns no rows - database

Question

Below is the part of my script.
The "set -e" will make the script exit whenever a negative return code comes from any of the commands.
But, when the below select statement returns no rows from the table, the script exits there itself (echo "Get Eg names end" is not executed). Which means the below command is giving negative return code.
db2 -x "SELECT EG_NAME FROM MS.CFG_CACHE_REFRESH WHERE
EG_RELOAD_UPD_BK2_TS < M_TABLE_UPD_TS AND CURRENT_TIME >= EG_RELOAD_START_TIME AND
CURRENT_TIME <= EG_RELOAD_END_TIME"
> /home/DummyUser/gm4/logs/MP_CACHE_REFRESH_TEMP_BK2.txt
If the select statement returns some rows, it works fine. The script doesn't exit and runs till the end.
My requirement is to exit if a genuine error occurs, like unable to connect database, invalid syntax etc.
If no rows are returned from the table, it should not be considered as an error.
Why am I getting a -ve return code for the select query not returning rows and how can I handle this?
Below is the part of the script:
#!/bin/ksh
set -e
brokername=$1
if [ "$#" -ne "1" ]
then
echo "Invalid arugments supplied"
echo "call the script using command:"
echo "MP_CACHE_REFRESH_BRK2.ksh <BrokerName>"
exit -1
fi
touch /home/DummyUser/gm4/logs/MP_CACHE_REFRESH_TEMP_BK2.txt
chmod 777 /home/DummyUser/gm4/logs/MP_CACHE_REFRESH_TEMP_BK2.txt
db2 CONNECT TO MSAPP USER DummyUser using paasss
db2 -x "SELECT EG_NAME FROM MS.CFG_CACHE_REFRESH WHERE EG_RELOAD_UPD_BK2_TS < M_TABLE_UPD_TS AND CURRENT_TIME >= EG_RELOAD_START_TIME AND CURRENT_TIME <= EG_RELOAD_END_TIME" > /home/DummyUser/gm4/logs/MP_CACHE_REFRESH_TEMP_BK2.txt
echo "Get Eg names end"

Answer 1

The problem is not negative return codes, it is any return code that is != 0. DB2 exits with:
- 0, success
- 1, no row found
- 2, warning (for example using existing index instead of creating a new one)
- 4, error (for example object not found)
- 8, system error (os related)
Unless you wrap db2 and return 0 for $? -lt 4 I don't see how you are going to success. Example on how to deal with db2 exit codes (-e removed)
db2 -x "SELECT EG_NAME FROM MS.CFG_CACHE_REF ..."
rc=$?
if [ $rc -ge 4 ]; then
...
EDIT: Alternative with sql stmts in separate file
Keeping all the sql in a separate file - say myfile.sql - you can do something like from your sh:
db2 -l myfile.log +c -s -tf myfile.sql
rc=$?
if [ $rc -ge 4 ]; then
echo "Error"
db2 rollback
exit 1
elif [ $rc -ge 1 ]; then
echo "Warning"
fi
db2 commit
exit 0
-s terminates execution on error ( -ge 4 ). You can find out what caused the problem by tailing the log file, tail -10 myfile.log. Beware that certain operations such as reorg will commit the ongoing transaction.