Ëæ»úÉú³ÉmysqlÊý ÌΪ0µÄä¯ÀÀÁ¿ ÏÂÔØÁ¿

update document_info set download_count=download_count+(SELECT 20+FLOOR(500 + (RAND() * 2000))) where download_count = 0

ÈôÒªÔÚ7 µ½ 12 µÄ·¶Î§（°üÀ¨7ºÍ12）Äڵõ½Ò»¸öËæ»úÕûÊý, ¿ÉʹÓÃÒÔÏÂÓï¾ä：

SELECT FLOOR(7 + (RAND() * 6));