CMPB_ASGN_KEY is an SAP Structure so does not store data like a database table does but can be used to process "Key for Campaign Assignment" Information within sap ABAP programs. This is done by declaring abap internal tables, work areas or database tables based on this Structure. These can then be used to store and process the required data appropriately.
i.e. DATA: wa_CMPB_ASGN_KEY TYPE CMPB_ASGN_KEY .
Below is the documentation avaialable and full details of the fields which make up this Structure.
|Data Type||length (Decimals)||Check table||Description||Conversion Routine|
|Sales and Distribution Document Number||ALPHA|
|Item number of the SD document|
|CAMPAIGN||CGPL_GUID16_R3||RAW||16||Generic project planning: GUID from external R/3 system|