Database schema consists of 3 tables:
The table utQ includes square identifier, square name. Note that non-painted square is black.
The table utV includes balloon identifier, balloon name, and paint color.
The table utB shows information on painting square with paint balloon and includes the square identifier, the balloon identifier, the paint quantity, and time of painting.
It should be noted that
Fig. Painting database schema
Some explanations to the scheme.
Identifiers of black squares are absent from utB table. It due to the fact that B_VOL does not allow NULL values and is strictly greater than zero. Thus, each record in utB table describes the fact of painting a square by a can (balloon), the black square (R=0, G=0, B=0) was not painted at all.
Constraints of the scheme allow simultaneous painting one square by several cans, as well as simultaneous painting the several squares with aid of one can. However these forbid painting one square by the same ballon at a time.