如何在 Oracle 中遍历分层数据并对同一层级的行进行排序?
问题描述:您需要从上到下遍历分层数据并对同一层级的行进行排序。
解决方案:通常的 ORDER BY 子句无法对同一层级的行进行排序。我们需要在 ORDER BY 子句中使用 SIBLINGS 子句。
此外，Oracle 提供了 CONNECT BY 子句来指定分层查询，即如何连接父节点和子节点;PRIOR 运算符用于定义父节点之间的连接条件;LEVEL 伪列用于指示当前行与根/父行之间的距离。
此外，我们可以使用 START WITH 子句来指示树形导航的起始位置。我们必须使用 PRIOR 运算符来指定父行中与子行链接列具有相同值的列。
为了遍历整个层级结构，请删除 START WITH 子句。这将获取所有学生及其教授、教授的教授(即院长)等，直至学院的最高经理/主任。
示例 1:对 professor_id = 102 的父行中处于同一层级的行进行排序，SQL 语句如下:
/*
Function - Identify the hierarchical/structure for the professor_id = 102
Tables Used - students
Data - documented below
*/
SELECT student_id,
level,
lpad('-',(level-1)*3) || first_name || ' ' || last_name AS full_name
FROM students
START WITH professor_id = 102
CONNECT BY professor_id = PRIOR student_id
ORDER SIBLINGS by first_name, last_name;
输出
103 1 BROWN MICHAEL 106 2 -DAVIS RICHARD 107 2 -GARCIA CHARLES 104 2 -JONES WILLIAM 105 2 -MILLER DAVID
示例 2:对父行中 professor_id 为 null 的层次结构中的同一级别的行进行排序 SQL:
/*
Function - Sort the rows at the same level in a hierarchy with in a Parent row
Tables Used - students
Data - documented below
*/
SELECT student_id,
level,
lpad('-',(level-1)*3) || first_name || ' ' || last_name AS full_name
FROM students
START WITH professor_id IS null
CONNECT BY professor_id = PRIOR student_id
ORDER SIBLINGS by first_name, last_name;
输出
100 1 SMITH JAMES 101 2 -JOHNSON JOHN 108 3 -RODRIGUEZ JOSEPH 111 4 -ANDERSON DANIEL 110 4 -MARTINEZ CHRISTOPHER 112 4 -TAYLOR PAUL 113 4 -THOMAS MARK 109 4 -WILSON THOMAS 102 2 -WILLIAMS ROBERT 103 3 -BROWN MICHAEL 106 4 -DAVIS RICHARD 107 4 -GARCIA CHARLES 104 4 -JONES WILLIAM 105 4 -MILLER DAVID
排序显然发生在层级结构的每一层。输出显示，在 SMITH JAMES 下，第 2 层级中的直接下属是 JOHNSON JOHN 和 WILLIAMS ROBERT，按字母顺序排列。在 JOHNSON JOHN 下，第 3 层级的下属也完全按字母顺序排列。
数据准备:用于此问题的数据如下所示。数据完全是虚构的，仅供演示之用。
示例
DROP TABLE students; COMMIT; CREATE TABLE students ( student_id NUMBER(6) , first_name VARCHAR2(20) , last_name VARCHAR2(25) , email VARCHAR2(40) , phone_number VARCHAR2(20) , join_date DATE , class_id VARCHAR2(20) , fees NUMBER(8,2) , professor_id NUMBER(6) , department_id NUMBER(4) ) ;
示例
CREATE UNIQUE INDEX stu_id_pk ON students (student_id) ;
INSERT INTO students VALUES (100,'SMITH','JAMES','SMITH.JAMES@notreal.com','111.111.1245',TO_DATE('17-06-2003','DD-MM-YYYY'),'INS_CHAIRMAN',24000,NULL,NULL);
INSERT INTO students VALUES (101,'JOHNSON','JOHN','JOHNSON.JOHN@notreal.com','111.111.1246',TO_DATE('21-09-2005','DD-MM-YYYY'),'INS_VP',17000,100,90);
INSERT INTO students VALUES (102,'WILLIAMS','ROBERT','WILLIAMS.ROBERT@notreal.com','111.111.1247',TO_DATE('13-01-2001','DD-MM-YYYY'),'INS_VP',17000,100,90);
INSERT INTO students VALUES (103,'BROWN','MICHAEL','BROWN.MICHAEL@notreal.com','111.111.1248',TO_DATE('03-01-2006','DD-MM-YYYY'),'INS_STAFF',9000,102,60);
INSERT INTO students VALUES (104,'JONES','WILLIAM','JONES.WILLIAM@notreal.com','111.111.1249',TO_DATE('21-05-2007','DD-MM-YYYY'),'INS_STAFF',6000,103,60);
INSERT INTO students VALUES (105,'MILLER','DAVID','MILLER.DAVID@notreal.com','111.111.1250',TO_DATE('25-06-2005','DD-MM-YYYY'),'INS_STAFF',4800,103,60);
INSERT INTO students VALUES (106,'DAVIS','RICHARD','DAVIS.RICHARD@notreal.com','111.111.1251',TO_DATE('05-02-2006','DD-MM-YYYY'),'INS_STAFF',4800,103,60);
INSERT INTO students VALUES (107,'GARCIA','CHARLES','GARCIA.CHARLES@notreal.com','111.111.1252',TO_DATE('07-02-2007','DD-MM-YYYY'),'INS_STAFF',4200,103,60);
INSERT INTO students VALUES (108,'RODRIGUEZ','JOSEPH','RODRIGUEZ.JOSEPH@notreal.com','111.111.1253',TO_DATE('17-08-2002','DD-MM-YYYY'),'CL_PHY',12008,101,100);
INSERT INTO students VALUES (109,'WILSON','THOMAS','WILSON.THOMAS@notreal.com','111.111.1254',TO_DATE('16-08-2002','DD-MM-YYYY'),'CL_MATH',9000,108,100);
INSERT INTO students VALUES (110,'MARTINEZ','CHRISTOPHER','MARTINEZ.CHRISTOPHER@notreal.com','111.111.1255',TO_DATE('28-09-2005','DD-MM-YYYY'),'CL_MATH',8200,108,100);
INSERT INTO students VALUES (111,'ANDERSON','DANIEL','ANDERSON.DANIEL@notreal.com','111.111.1256',TO_DATE('30-09-2005','DD-MM-YYYY'),'CL_MATH',7700,108,100);
INSERT INTO students VALUES (112,'TAYLOR','PAUL','TAYLOR.PAUL@notreal.com','111.111.1257',TO_DATE('07-03-2006','DD-MM-YYYY'),'CL_MATH',7800,108,100);
INSERT INTO students VALUES (113,'THOMAS','MARK','THOMAS.MARK@notreal.com','111.111.1258',TO_DATE('07-12-2007','DD-MM-YYYY'),'CL_MATH',6900,108,100);
COMMIT;
