DB2/UDB batch query

I need to execute a batch DB2/UDB command under AIX which counts the number of records in a table.  The resulting value will be used subsequently in the script.

A simple example under MS-SQL Server would be as follows from within a DOS batch file:

  isql -S CMC_NT1 -d CSTI -U sa -P -Q "EXIT(select count(*) from Products)" > NUL
  echo %ERRORLEVEL%

where ERRORLEVEL will contain the results of the SELECT statement.

I'm new to DB2/UDB and need to know how I can execute a query using the db2 command line utility and transfer the resulting value back to the operating system level (exit code?) for later use.
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llewelmAsked:
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jbrickardConnect With a Mentor Commented:
Using the EXPORT utility would be one way, but then the result has to be read back from a file.

On UNIX however, you can just capture the result of a standard DB2 CLP command (with appropriate formatting options) in a shell variable.

For example, assuming your CLP session has default options, the following script should work:

#/bin/ksh
db2 "CONNECT TO sample USER youruser USING yourpassword"
result=`db2 -x "SELECT COUNT(*) FROM yourschema.yourtable"`
echo $?
echo $result

So long as $? returns 0, $result should contain the single value returned by the db2 CLP command contained between the ` marks.  The -x CLP option suppresses column headings, thereby ensuring that only a single line containing a single number is returned (so long as your SQL is correct).

My Korn shell knowledge is not that strong, so there may possibly be a slight error in the above - but it's definitely along the right lines (I've used this for real).


Jeremy Rickard
DB2 UDB specialist
United Systems(UK) Ltd.
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pluimCommented:
You can check the return code of the db2 operation by evaluating "$?", e.g.

-------------------------------------begin samplescript.ksh
#!/usr/bin/ksh

db2 "connect to mydb user myuser using mypassword"
if [ $? != 0 ]; then
  print "An error occurred when connecting to the database"
  exit -1
fi

db2 "select count(*) from products" > productcount.txt
if [ $? != 0 ]; then
  print "An error occurred when counting the products"
  exit -1
fi

exit 0
---------------------------------------end samplescript.ksh
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llewelmAuthor Commented:
According to the DB2/UDB documentation, the exit code from the db2 command is 0, 1, 2, 4 or 8 indicating the relative level of success in executing the command, not the actual record count as I'm looking for.

Referring to your specific example, I could parse the value out of the 'productcount.txt' file.  However, that is way more trouble than it's really worth.
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pluimCommented:
Sorry, I misunderstood the question. Your reference to the exit code led me to believe you wanted to know whether the operation succeeded, not the actual record count.

I agree that parsing out the value can be a pain, since you have to account for the column header and separator line. It's a lot easier when you use the export facility, e.g.

db2 "export to count.txt of del select count(*) from products"
prodcount=`cat count.txt`
rm count.txt

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pluimCommented:
Jeremy,

My version of DB/2 (6.1) doesn't recognize the -x option. Is this new in v7? This would be a really useful flag to have - much more elegant than using a temporary file.
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llewelmAuthor Commented:
I don't have the -x command available to me either.  Is there an alternative?
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jbrickardCommented:
I don't have a copy of v6 to hand, but I'm pretty certain that -x has been supported always (in DB2 UDB)

To double check, you can type:

  db2 LIST COMMAND OPTIONS at the command prompt

-x should be displayed (near the bottom).

I've just tried a simple script on Linux, pretty much as before, except I had the ksh directive wrong:

  #!/usr/bin/ksh
  db2 "CONNECT TO SAMPLE USER rickard USING xxx"
  result=`db2 -x "SELECT COUNT(*) FROM SYSCAT.TABLES"`
  echo return code = $?
  echo result = $result

The output is:

  return code = 0
  result = 150

Have you tried this out?  If so and you are still having problems, send me your script and the output, and I'll take a look.
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llewelmAuthor Commented:
We're running v6.1 here and the -x option is not available.  The result is a message indicating an invalid option.

However, removing the -x from the test script still results in the correct result.  Thanks for the help...
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