sql计算当前年较比上一年的销售量的增长率(当年的一道sql笔试题)

create table YEAR_SALES(  YEAR     VARCHAR2(4),  QUANTITY NUMBER);prompt Loading YEAR_SALES...insert into YEAR_SALES (YEAR, QUANTITY)values ('2001', 100);insert into YEAR_SALES (YEAR, QUANTITY)values ('2002', 200);insert into YEAR_SALES (YEAR, QUANTITY)values ('2003', 220);insert into YEAR_SALES (YEAR, QUANTITY)values ('2004', 260);insert into YEAR_SALES (YEAR, QUANTITY)values ('2005', 300);insert into YEAR_SALES (YEAR, QUANTITY)values ('2006', 330);commit;select t1.year, t1.quantity / t2.quantity increase_rate  from year_sales t1 inner join year_sales t2 on t1.year - 1 = t2.year