SQL技巧：WITH RECURSIVE遞歸運算

累加求和運算

-- 計算遞歸
WITH RECURSIVE t(n) AS (
    VALUES (1)
  UNION ALL
    SELECT n+1 FROM t WHERE n < 100
)
SELECT sum(n) FROM t;

遞歸拆分數據-分表

-- 測試工資遞歸
create table company (
    id int ,
    name varchar (60),
    age int ,
    address varchar (30),
    salary int
);

insert into company values(1,'Paul',32,'California',20000);
insert into company values(2,'Allen',25, 'Texas',15000);
insert into company values(3,'Teddy',23,'Norway',20000);
insert into company values(4,'Mark',25,'Rich-Mond',65000);
insert into company values(5,'David',27,'Texas',85000);
insert into company values(6,'Kim',22,'South-Hall',45000);
insert into company values(7,'James',24,'Houston',10000);


--找到小於20000的薪金總和
WITH RECURSIVE t(n) AS (
        VALUES (0)
        UNION ALL
        SELECT salary FROM company WHERE salary < 20000
)
SELECT SUM(n) FROM t

--刪除指定的公司行,RETURNING子句返回它們的內容;然後主查詢讀取輸出，並將其插入到COMPANY1 表：
 
CREATE TABLE COMPANY1(
   ID INT PRIMARY KEY     NOT NULL,
   NAME           TEXT    NOT NULL,
   AGE            INT     NOT NULL,
   ADDRESS        CHAR(50),
   SALARY         REAL
);
WITH moved_rows AS (
    DELETE FROM COMPANY
    WHERE
        SALARY >= 30000
    RETURNING *
)
INSERT INTO COMPANY1 (SELECT * FROM moved_rows);
 
SELECT * FROM COMPANY;
SELECT * FROM COMPANY1;

省市縣區域字符串拼接

-- 省市區域字符串連接拼接測試
create table tb(id varchar(3) , pid varchar(3) , name varchar(10)); 
insert into tb values('002' , 0 , '浙江省'); 
insert into tb values('001' , 0 , '廣東省'); 
insert into tb values('003' , '002' , '衢州市');  
insert into tb values('004' , '002' , '杭州市') ; 
insert into tb values('005' , '002' , '湖州市');  
insert into tb values('006' , '002' , '嘉興市') ; 
insert into tb values('007' , '002' , '寧波市');  
insert into tb values('008' , '002' , '紹興市') ; 
insert into tb values('009' , '002' , '台州市');  
insert into tb values('010' , '002' , '溫州市') ; 
insert into tb values('011' , '002' , '麗水市');  
insert into tb values('012' , '002' , '金華市') ; 
insert into tb values('013' , '002' , '舟山市');  
insert into tb values('014' , '004' , '上城區') ; 
insert into tb values('015' , '004' , '下城區');  
insert into tb values('016' , '004' , '拱墅區') ; 
insert into tb values('017' , '004' , '餘杭區') ; 
insert into tb values('018' , '011' , '金東區') ; 
insert into tb values('019' , '001' , '廣州市') ; 
insert into tb values('020' , '001' , '深圳市') ;


with RECURSIVE cte as
(
select a.id,cast(a.name as varchar(100)) from tb a where id='002'
union all 
select k.id,cast(c.name||'>'||k.name as varchar(100)) as name  from tb k inner join cte c on c.id = k.pid
)select id,name from cte ;

MYSQL和POSTGRESQL 都支持WITH RECURSIVE語法：

https://www.cnblogs.com/kungfupanda/p/5628769.html

應用示例

查看組織機構遞歸

-- 同表遞歸查詢
with RECURSIVE orgIdRelations as
(
select a.i_orgid,cast(a.i_orgid as varchar(100)) as parentIds from xh_ht.fs_yw_base_org a where a.i_orgid =1
   union all 
select k.i_orgid, cast(c.parentIds||','||k.i_orgid as varchar(100)) as parentIds  
   from xh_ht.fs_yw_base_org k inner join orgIdRelations c on c.i_orgid = k.i_orgpid
)
select i_orgid,parentIds from orgIdRelations ;

查看組織機構名稱遞歸

-- 同表遞歸查詢
with RECURSIVE orgNames as
(
select a.i_orgid,cast(a.c_orgname as varchar(1000)) as orgName from xh_ht.fs_yw_base_org a where a.i_orgid=1
   union all 
select k.i_orgid,cast(c.orgName||'>'||k.c_orgname as varchar(1000)) as orgName  
   from xh_ht.fs_yw_base_org k inner join orgNames c on c.i_orgid = k.i_orgpid
)
select i_orgid,orgName from orgNames ;