MQRECEIVECLOB scalar function

The MQRECEIVECLOB function returns a message from a specified IBM® MQ location and removes the message from the queue.

Read syntax diagramSkip visual syntax diagramMQRECEIVECLOB(receive-service,service-policy,correl-id)

The schema is DB2MQ.

The MQRECEIVECLOB function returns a message from the IBM MQ location that is specified by receive-service, using the quality-of-service policy that is defined in service-policy. Performing this operation removes the message from the queue that is associated with receive-service.

receive-service
An expression that returns a value that is a built-in character string or graphic string data type that is not a LOB. The value of the expression must not be an empty string or a string with trailing blanks. The expression must have an actual length that is no greater than 48 bytes. The value of the expression must refer to a service point that is defined in the DB2MQ.MQSERVICE table. A service point is a logical end-point from which a message is sent or received. A service point definition includes the name of the IBM MQ queue manager and the name of the queue. See IBM MQ Application Messaging Interface for more details.

If receive-service is not specified or is the null value, DB2.DEFAULT.POLICY is used.

service-policy
An expression that returns a value that is a built-in character string or graphic string data type that is not a LOB. The value of the expression must not be an empty string or a string with trailing blanks. The expression must have an actual length that is no greater than 48 bytes. The value of the expression must refer to a service policy that is defined in the DB2MQ.MQPOLICY table. A service policy specifies a set of quality-of-service options that are to be applied to this messaging operation. These options include message priority and message persistence. See IBM MQ Application Messaging Interface for more details.

If service-policy is not specified or is the null value, DB2.DEFAULT.POLICY is used.

correl-id
An expression that returns a value that is a built-in character string or graphic string data type that is not a LOB. The expression must have an actual length that is no greater than 24 bytes. The value of the expression specifies the correlation identifier that is associated with this message. A correlation identifier is often specified in request-and-reply scenarios to associate requests with replies. Only those messages with a matching correlation identifier are returned.

A fixed length string with trailing blanks is considered a valid value. However, when the correl-id is specified on another request such as MQSEND, the correl-id must be specified the same to be recognized as a match. For example, specifying a value of 'test' for correl-id for this function does not match a correl-id value of 'test   ' (with trailing blanks) specified earlier on an MQSEND request.

If correl-id is not specified, is an empty string, or is the null value, a correlation identifier is not used, and the message at the beginning of the queue is returned.

The result of the function is a CLOB with a length attribute of 1 MB. The result can be null. If no messages are available to be returned, the result is the null value.

The CCSID of the result is the system CCSID that was in effect at the time that the IBM MQ function was installed into Db2.

Examples

Example 1: Retrieve the message from the beginning of the queue specified by the default service (Db2.DEFAULT.SERVICE), using the default policy (Db2.DEFAULT.POLICY)
   SELECT MQRERECEIVECLOB()
     FROM SYSIBM.SYSDUMMY1;
The message at the beginning of the queue is returned as a CLOB and is deleted from the queue. The queue is specified by the default service and using the default policy.
Example 2: Retrieve the message from the beginning of the queue specified by the service MYSERVICE, using the policy (Db2.DEFAULT.POLICY)
   SELECT MQRECEIVECLOB('MYSERVICE')
     FROM SYSIBM.SYSDUMMY1;
The message at the beginning of the queue is returned as a CLOB and is deleted from the queue. The queue is specified by MYSERVICE and using the default policy.
Example 3: Retrieve the message from the beginning of the queue specified by the service MYSERVICE, using the policy MYPOLICY
   SELECT MQRECEIVECLOB('MYSERVICE','MYPOLICY')
     FROM SYSIBM.SYSDUMMY1;
The message at the beginning of the queue is returned as a CLOB and is deleted from the queue. The queue is specified by MYSERVICE and using the policy MYPOLICY.
Example 4: Retrieve the first message from the beginning of the queue with a correlation identifier that matches '1234' from the queue specified by the service MYSERVICE, using the policy MYPOLICY
   SELECT MQRECEIVECLOB('MYSERVICE','MYPOLICY','1234')
     FROM SYSIBM.SYSDUMMY1;
The first message at the beginning of the queue with a correlation identifier with '1234' is returned as a CLOB and is deleted from the queue. The queue is specified by MYSERVICE and using the policy MYPOLICY.