What is meanung of NULL in the timefield column? How records with NULL is sorted relativly to other records?

>there can be 6 records for morning and 6 records for afternoon, any others are ignored.
>
>>How many records could be in each group?
>>
>>>
>>> This query is suppose to combine another table into a wide table. From my questions before about getting records from going down to going across:
>>>

>>>id    timefield         field1  field2  field3   field4
>>>1      01/01/00 15:45    hi      0       check   field
>>>1      01/01/00 7:48     bye     1       double  main
>>>2      01/01/00 14:51    hi      0       check   field
>>>2      01/01/00 8:48     bye     1       NULL    main
>>>3      NULL              get     0       fake    NULL
>>>3      NULL              get2    1       fake    NULL
>>>4      01/01/00 16:05    get1    1       fake    NULL
>>>

>>>need to get into this form: