Question

o u 10 1) a) fo vasuiable ohat would Luytn tields it-the value us- mull On Some plitatins, txpla haue mumbe b) uouu di d srepresentation Such-that ovenhiad tr fur a null attn buti ù e

Answer 1

1a. In the variable-length record representation, bitmaps are used to represent the presence of a null value in an attribute. Usually, the length and offset of the null valued attributes are stored as negative. But the data stored in the offset and length is usually ignored because of using the bitmap in the record representation to identify the null valued attributes.

1b. For the applications where most of the attributes are null, the record representation is modified by placing the null bitmap at the beginning of the record. In these records, for the null valued attribute, the length and offset, and the values are not stored. The bitmap alone represents by a single bit that the attribute is null. This helps to save storage space and cost to extract attributes of the record.