IV44537: DOC DOCUMENTATION FOR MQL QUERIES USING != (NOT EQUAL TO) OR NOT KEYWORD NEEDS TO BE ADDED.

APAR status

• Closed as documentation error.

Error description

• There is a common misconception that the count returned from
  the following API find command:
  ./api.sh -u <admin> -p <pass> find --count "select * from
  ComputerSystem"
  
  should equal the sum of the results from the following two API
  find commands:
  ./api.sh -u <admin> -p <pass> find --count "select *
  from ComputerSystem where manufacturer == 'IBM'"
  and
  ./api.sh -u <admin> -p <pass> find --count "select *
  from ComputerSystem where manufacturer != 'IBM'"
  
  However, this is not an accurate assumption as a comparison of
  NULL values evaluates to 'unknown'.  Thus, all records with
  NULL attribute values will be excluded from the result.
  
  Documentation for 'Model Query Language overview' should be
  enhanced with description and examples of queries that use not
  equal to operator:
  
  In queries that use not equal to operator ('!=', 'not-equals')
  like:
  select * from ComputerSystem where manufacturer != 'IBM'
  or
  select * from ComputerSystem where not(manufacturer == 'IBM')
  
  one may expect that the results will also contain
  ComputerSystems with manufacturer set to NULL. However, when
  NULL value is used in the comparison the result is evaluated to
  'unknown', thus it is excluded from the result. The correct way
  to select all the ComputerSystems thathave manufacturer other
  than IBM is to use the following query:
  
  select * from ComputerSystem where manufacturer != 'IBM' or
  manufacturer is-null.
  
  Table 1 in document
  
  http://pic.dhe.ibm.com/infocenter/db2luw/v9r7/topic/com.ibm.db2.
  luw.sql.ref.doc/doc/r0000754.html
  contains information how search conditions are
  evaluated when there is 'unknown' value.
  
  Please also add an example of using the --count parameter with
  the API find as shown above.
  

Local fix

• n/a
  

Problem summary

• DOCUMENTATION FOR MQL QUERIES USING != (NOT EQUAL TO) OR   NOT
  KEYWORD NEEDS TO BE ADDED.
  

Problem conclusion

• Link with the changes:
  http://eden1.tivlab.austin.ibm.com:9997/help/topic/com.ibm.taddm
  .doc_721fp4/SDKDevGuide/c_cmdbsdk_mql_introducing.html
  

Temporary fix

Comments

APAR Information

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Fix information

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