oracle 语法兼容性,GaussDB(DWS)中Oracle不兼容语法修改集
1、递归语法
单表递归
Oracle：
create table tb_recursive(id int,parent_id int);
insert into tb_recursive values(0,'');
insert into tb_recursive values(1,0);
insert into tb_recursive values(11,1);
insert into tb_recursive values(12,1);
insert into tb_recursive values(111,11);
insert into tb_recursive values(2,0);
insert into tb_recursive values(21,2);
insert into tb_recursive values(22,2);
insert into tb_recursive values(222,22);
insert into tb_recursive values(211,21);
insert into tb_recursive values(212,21);
select id,parent_id,level lvl from tb_recursive connect by prior id=parent_id start with parent_id is null order by id;
Gauss：
create table tb_recursive(id int,parent_id int);
insert into tb_recursive values(0,'');
insert into tb_recursive values(1,0);
insert into tb_recursive values(11,1);
insert into tb_recursive values(12,1);
insert into tb_recursive values(111,11);
insert into tb_recursive values(2,0);
insert into tb_recursive values(21,2);
insert into tb_recursive values(22,2);
insert into tb_recursive values(222,22);
insert into tb_recursive values(211,21);
insert into tb_recursive values(212,21);
with recursive r1 as (
select id,parent_id,1 as lvl
from tb_recursive
where parent_id is null
union all
select t.id,t.parent_id,t1.lvl+1 as lvl
from tb_recursive t,r1 t1
where t.parent_id=t1.id)
select id,parent_id,lvl from r1 order by id;
Oracle:
select id,parent_id,level lvl from tb_recursive connect by id=prior parent_id start with parent_id is null order by id;
Gauss:
with recursive r1 as (
select id,parent_id,1 as lvl
from tb_recursive
where parent_id is null
union all
select t.id,t.parent_id,t1.lvl+1 as lvl
from tb_recursive t,r1 t1
where t.id=t1.parent_id)
select id,parent_id,lvl from r1 order by id;
sys_connect_by_path
Oracle:
select id,parent_id,sys_connect_by_path(id,' > ') path,level lvl from tb_recursive connect by prior id= parent_id start with parent_id is null order by id;
Gauss:
with recursive r1 as (
select id,parent_id,' > '||id path,1 as lvl
from tb_recursive
where parent_id is null
union all
select t.id,t.parent_id,t1.path||' > '||t.id path,t1.lvl+1 as lvl
from tb_recursive t,r1 t1
where t.parent_id=t1.id)
select id,parent_id,path,lvl from r1 order by id;
order siblings by
Oracle:
select id,parent_id,level lvl from tb_recursive connect by prior id=parent_id start with parent_id is null order siblings by id;
Gauss:
with recursive r1 as (
select id,parent_id,1 as lvl,lpad(id,4,0)||lpad(ctid||xc_node_id::text,20,0) sortno
from tb_recursive
where parent_id is null
union all
select t.id,t.parent_id,t1.lvl+1 as lvl,t1.sortno||lpad(t.id,4,0)||lpad(ctid||xc_node_id::text,20,0) sortno
from tb_recursive t,r1 t1
where t.parent_id=t1.id)
select id,parent_id,lvl from r1 order by sortno;
connect_by_root
Oracle:
select id,parent_id,connect_by_root(parent_id) as rid,level lvl from tb_recursive connect by prior id=parent_id start with parent_id =2 order by id;
Gauss:
with recursive r1 as (
select id,parent_id,parent_id rid,1 as lvl
from tb_recursive
where parent_id =2
union all
select t.id,t.parent_id,t1.rid,t1.lvl+1 as lvl
from tb_recursive t,r1 t1
where t.parent_id=t1.id)
select id,parent_id,rid,lvl from r1 order by id;
connect by前有where
Oracle:
select id,parent_id,level lvl from tb_recursive where parent_id = 1 connect by prior id=parent_id start with parent_id is null order by id;
Gauss:
with recursive r1 as (
select id,parent_id,1 as lvl
from tb_recursive
where parent_id is null
union all
select t.id,t.parent_id,t1.lvl+1 as lvl
from tb_recursive t,r1 t1
where t.parent_id=t1.id)
select id,parent_id,lvl from r1 where parent_id =1 order by id;
2、Rownum
select list中
Oracle:
select id,parent_id,rownumfrom tb_recursive order by 3;
Gauss:
select id,parent_id,row_number() over() from tb_recursive order by 3;
where条件中
Oracle:
select id,parent_id from tb_recursive where rownum =1order by id;
Gauss:
select id,parent_id from tb_recursive order by idlimit 1;
sql语句中有order by
Oracle:
select id from (select id,parent_id from tb_recursive order by id desc) whererownum =1;
Gauss:
select id from tb_recursive order by id desc limit 1;
sql语句中有count
Oracle:
select count(1) from (select id,parent_id from tb_recursive where id = 1)where rownum =1;
Gauss:
select count(1) from (select id,parent_id from tb_recursive where id = 1 limit 1);
sql语句中有max/min
Oracle:
selectmax(id)from tb_recursive where parent_id=21 and rownum =1;
select min(id) from tb_recursive where parent_id=21 and rownum =1;
Gauss:
select id from tb_recursive where parent_id=21 order by id limit 1;
3、Max/Min...keep语法
单表max,dense_rank last
Oracle:
select max(id) keep (dense_rank last order by parent_id) from tb_recursive;
Gauss:
select id from tb_recursive order by parent_id desc,id desc limit 1;
单表max,dense_rank first
Oracle:
select max(id)keep (dense_rank first order by parent_id) from tb_recursive;
Gauss:
select id from tb_recursive order by parent_id asc,id desc limit 1;
单表min,dense_rank last
Oracle:
select min(id)keep (dense_rank last order by parent_id) from tb_recursive;
Gauss:
select id from tb_recursive order by parent_id desc,id asc limit 1;
单表min,dense_rank first
Oracle:
select min(id)keep (dense_rank first order by parent_id) from tb_recursive;
Gauss:
select id from tb_recursive order by parent_id asc,id asc limit 1;
4、pivot语法
测试表及数据：
drop table if exists tb_test;
create table tb_test(a int,b int);
insert into tb_test values(1,1),(1,1),(1,2),(1,3),(1,4),(2,1),(2,2),(2,3),(2,2),(2,4),(2,5),(2,6);
Oracle:
select * from
(select a,b,count(*) cnt from tb_test group by a,b) t
pivot(sum(cnt) for a in (1 c,2 d,3 e,4 f));
Gauss:
select b,sum(case a when 1 then cnt end) C,
sum(case a when 2 then cnt end) D,
sum(case a when 3 then cnt end) E,
sum(case a when 4 then cnt end) F
from (select a,b,count(*) cnt from tb_test group by a,b)
group by b;