MQRECEIVEALLCLOB table function

The MQRECEIVEALLCLOB function returns a table that contains the messages and message metadata from a specified IBM® MQ location and removes the messages from the queue.

Notes:

¹ The comma is required before num-rows when any of the preceding arguments to the function are specified.

The schema is DB2MQ.

The MQRECEIVEALLCLOB function returns a table containing the messages and message metadata 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 messages 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.

num-rows

An expression that returns a value that is a SMALLINT or INTEGER data type whose value is a positive integer or zero. The value of the expression specifies the maximum number of messages to return.

If num-rows is not specified or if the value of the expression is zero, all available messages are returned.

The result of the function is a table with the format shown in the following table. All of the columns are nullable.

Table 1. Format of resulting table for MQRECEIVEALLCLOB
Column name	Data type	Contains
MSG	CLOB(1M)	The contents of the IBM MQ message
CORRELID	VARCHAR(24)	The correlation ID that is used to relate messages
TOPIC	VARCHAR(40)	The topic that the message was published with, if available
QNAME	VARCHAR(48)	The name of the queue from which the message was received
MSGID	CHAR(24)	The unique message identifier assigned by IBM MQ
MSGFORMAT	VARCHAR(8)	The format of the message, as defined by IBM MQ

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 all the messages from the queue specified by the default service (Db2.DEFAULT.SERVICE), using the default policy (Db2.DEFAULT.POLICY)

   SELECT * FROM TABLE (MQRECEIVEALLCLOB()) AS T;

The messages and all the metadata are returned as a table, and the messages are removed.

Example 2

Retrieve all the messages from the beginning of the queue specified by the service MYSERVICE, using the policy (Db2.DEFAULT.POLICY)

   SELECT T.MSG, T.CORRELID
     FROM TABLE (MQRECEIVEALLCLOB('MYSERVICE')) AS T;

Only the MSG and CORRELID columns are returned as a table, and the messages removed from the queue.

Example 3

Retrieve all the messages from the queue specified by the service MYSERVICE, using the policy "MYPOLICY", with a correlation identifier of '1234'

   SELECT *
     FROM TABLE (MQRECEIVEALLCLOB('MYSERVICE','MYPOLICY','1234')) AS T;

All columns are returned, and the messages removed from the queue.

Example 4

Retrieve the first 10 messages from the beginning of the queue specified by the default service (Db2.DEFAULT.SERVICE), using the default policy (Db2.DEFAULT.POLICY)

   SELECT *
     FROM TABLE (MQRECEIVEALLCLOB(10)) AS T;

All columns are returned, and the messages removed from the queue.