Export DB2 select to CSV with headhers - csv

Question

I am trying to export DB2 select with headhers. But without any success, my actual code is:
db2 "EXPORT TO /tmp/result5.csv OF DEL MODIFIED BY NOCHARDEL
SELECT 1 as id, 'DEVICE_ID', 'USER_ID' from sysibm.sysdummy1
UNION ALL (SELECT 2 as id, DEVICE_ID, USER_ID FROM MOB_DEVICES) ORDER BY id"
which is not working (I suggest because USER_ID is INTEGER), when I change it for:
db2 "EXPORT TO /tmp/result5.csv OF DEL MODIFIED BY NOCHARDEL
SELECT 1 as id, 'DEVICE_ID', 'PUSH_ID' from sysibm.sysdummy1
UNION ALL (SELECT 2 as id, DEVICE_ID, PUSH_ID FROM MOB_DEVICES) ORDER BY id"
It works, DEVICE_ID and PUSH_ID are both VARCHAR.
MOB_DEVICE TABLE Any suggest how to solve this?
Thanks for advice.

Answer 1

DB2 will not export a CSV file with the headers, because the headers will be included as data. Normally, CSV file is for storage not viewing. If you want to view a file with its headers you have the following options:
Export to IXF file, but this file is not a flat file. You will need a spreadsheet to view it.
Export to a CSV file and include the headers by:
Select the columns names from the name, and then perform an extra step to add it to the file. You can use the describe command or perform a select on syscat.columns for this purpose, but this process is manual.
Perform a select union, in one part the data and in the other part the headers.
Perform a select and take the output to a file. Do not use export.
select * from myTable > myTable

Answer 2

Ignoring the EXPORT, thus just looking exclusively at the problematic UNION ALL query:
The DB2 SQL will want to conform the data of the mismatched data-types, into the numeric data-type; in this scenario, into the INTEGER data-type. Because conspicuously, the literal string value 'USER_ID' is not a valid representation of numeric value, that value can not be cast into an INTEGER value.
However, one can explicitly request to reverse that casting [whereby SQL wants to convert from string into numeric], to ensure that the SQL obeys the desired effect, to convert the INTEGER values from the column into VARCHAR values; i.e. explicit casting can ensure the data-types between the common columns of the UNION will be compatible, by forcing the values from the INTEGER column to match the data-type of the literal\constant character-string value of 'USER_ID':
with
mob_devices (DEVICE_ID, USER_ID, PUSH_ID) as
( values( varchar('dev', 1000 ), int( 1 ), varchar('pull', 1000) ) )
( SELECT 1 as id, 'DEVICE_ID', 'USER_ID'
from sysibm.sysdummy1
)
UNION ALL
( SELECT 2 as id, DEVICE_ID , cast( USER_ID as varchar(1000) )
FROM MOB_DEVICES
)
ORDER BY id