The "NULL" Value problem of The Visual FoxPro
Zhang Guo-tuan · Jilin Normal University Journal · 2005
NULL Value is a important concept of visual FoxPro, we can use NULL in looking for data. Because NULL is not the data in any mean, the way of importing NULL into FoxPro chart or freedom chart is different from the way of importing other kinds of data. The right way of importing NULL into of the phase in the chart was given in the present paper, and point out the wrong that will appear when we use the other ways of importing data to import the NULL value.