sql代码
复制代码 代码如下:
create table test(a varchar2( 20),b varchar2 (20),c number,d varchar2 (20))
insert into test values( ‘a1′,’b1’ ,1, ‘t’);
insert into test values( ‘a3′,’b3’ ,3, ‘t’);
insert into test values( ‘a4′,’b4’ ,4, ‘t’);
insert into test values( ‘a2′,’b2’ ,2, ‘t’);
insert into test values( ‘xx’,’xx’ ,5, ‘x’);
insert into test values( ‘a1′,’b1’ ,1, ‘t’);
insert into test values( ‘a3′,’b3’ ,3, ‘t’);
insert into test values( ‘a4′,’b4’ ,4, ‘t’);
insert into test values( ‘a2′,’b2’ ,2, ‘t’);
insert into test values( ‘xx’,’xx’ ,5, ‘x’);
commit;
1.select a,b, sum(c) from test where d= ‘t’ group by a,b order by a,b;
2.select a,b, sum(c) from test where d= ‘t’ group by b,a order by a,b;
总结：对于1，2而言，结果应该是一样的，但是分组的顺序不同，sql的性能应该也是不同的。