oracle group by语句实例测试

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。

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