Oracle PL/SQL Tutorial/Query Select/Level
Uses the COUNT() function and LEVEL to get the number of levels in the tree
SQL>
SQL>
SQL>
SQL>
SQL> -- create demo table
SQL> create table Employee(
2 EMPNO NUMBER(3),
3 ENAME VARCHAR2(15 BYTE),
4 HIREDATE DATE,
5 ORIG_SALARY NUMBER(6),
6 CURR_SALARY NUMBER(6),
7 REGION VARCHAR2(1 BYTE),
8 MANAGER_ID NUMBER(3)
9 )
10 /
Table created.
SQL>
SQL> create table job (
2 EMPNO NUMBER(3),
3 jobtitle VARCHAR2(20 BYTE)
4 )
5 /
Table created.
SQL>
SQL> insert into job (EMPNO, Jobtitle) values (1,"Tester");
1 row created.
SQL> insert into job (EMPNO, Jobtitle) values (2,"Accountant");
1 row created.
SQL> insert into job (EMPNO, Jobtitle) values (3,"Developer");
1 row created.
SQL> insert into job (EMPNO, Jobtitle) values (4,"COder");
1 row created.
SQL> insert into job (EMPNO, Jobtitle) values (5,"Director");
1 row created.
SQL> insert into job (EMPNO, Jobtitle) values (6,"Mediator");
1 row created.
SQL> insert into job (EMPNO, Jobtitle) values (7,"Proffessor");
1 row created.
SQL> insert into job (EMPNO, Jobtitle) values (8,"Programmer");
1 row created.
SQL> insert into job (EMPNO, Jobtitle) values (9,"Developer");
1 row created.
SQL>
SQL>
SQL> -- prepare data
SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (1, "Jason", to_date("19960725","YYYYMMDD"), 1234, 8767, "E", 2)
3 /
1 row created.
SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (2, "John", to_date("19970715","YYYYMMDD"), 2341, 3456, "W", 3)
3 /
1 row created.
SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (3, "Joe", to_date("19860125","YYYYMMDD"), 4321, 5654, "E", 3)
3 /
1 row created.
SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (4, "Tom", to_date("20060913","YYYYMMDD"), 2413, 6787, "W", 4)
3 /
1 row created.
SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (5, "Jane", to_date("20050417","YYYYMMDD"), 7654, 4345, "E", 4)
3 /
1 row created.
SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (6, "James", to_date("20040718","YYYYMMDD"), 5679, 6546, "W", 5)
3 /
1 row created.
SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (7, "Jodd", to_date("20030720","YYYYMMDD"), 5438, 7658, "E", 6)
3 /
1 row created.
SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION)
2 values (8, "Joke", to_date("20020101","YYYYMMDD"), 8765, 4543, "W")
3 /
1 row created.
SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION)
2 values (9, "Jack", to_date("20010829","YYYYMMDD"), 7896, 1232, "E")
3 /
1 row created.
SQL>
SQL>
SQL>
SQL> -- display data in the table
SQL> select * from Employee
2 /
EMPNO ENAME HIREDATE ORIG_SALARY CURR_SALARY R MANAGER_ID
---------- --------------- --------- ----------- ----------- - ----------
1 Jason 25-JUL-96 1234 8767 E 2
2 John 15-JUL-97 2341 3456 W 3
3 Joe 25-JAN-86 4321 5654 E 3
4 Tom 13-SEP-06 2413 6787 W 4
5 Jane 17-APR-05 7654 4345 E 4
6 James 18-JUL-04 5679 6546 W 5
7 Jodd 20-JUL-03 5438 7658 E 6
8 Joke 01-JAN-02 8765 4543 W
9 Jack 29-AUG-01 7896 1232 E
9 rows selected.
SQL> select * from job
2 /
EMPNO JOBTITLE
---------- --------------------
1 Tester
2 Accountant
3 Developer
4 COder
5 Director
6 Mediator
7 Proffessor
8 Programmer
9 Developer
9 rows selected.
SQL>
SQL> SELECT COUNT(DISTINCT LEVEL)
2 FROM employee
3 START WITH empno = 1
4 CONNECT BY PRIOR empno = manager_id;
COUNT(DISTINCTLEVEL)
--------------------
1
SQL>
SQL>
SQL> -- clean the table
SQL> drop table Employee
2 /
Table dropped.
SQL> drop table job
2 /
Table dropped.
SQL>
Using the LEVEL Pseudo-Column
SQL>
SQL>
SQL>
SQL>
SQL> -- create demo table
SQL> create table Employee(
2 EMPNO NUMBER(3),
3 ENAME VARCHAR2(15 BYTE),
4 HIREDATE DATE,
5 ORIG_SALARY NUMBER(6),
6 CURR_SALARY NUMBER(6),
7 REGION VARCHAR2(1 BYTE),
8 MANAGER_ID NUMBER(3)
9 )
10 /
Table created.
SQL>
SQL> create table job (
2 EMPNO NUMBER(3),
3 jobtitle VARCHAR2(20 BYTE)
4 )
5 /
Table created.
SQL>
SQL> insert into job (EMPNO, Jobtitle) values (1,"Tester");
1 row created.
SQL> insert into job (EMPNO, Jobtitle) values (2,"Accountant");
1 row created.
SQL> insert into job (EMPNO, Jobtitle) values (3,"Developer");
1 row created.
SQL> insert into job (EMPNO, Jobtitle) values (4,"COder");
1 row created.
SQL> insert into job (EMPNO, Jobtitle) values (5,"Director");
1 row created.
SQL> insert into job (EMPNO, Jobtitle) values (6,"Mediator");
1 row created.
SQL> insert into job (EMPNO, Jobtitle) values (7,"Proffessor");
1 row created.
SQL> insert into job (EMPNO, Jobtitle) values (8,"Programmer");
1 row created.
SQL> insert into job (EMPNO, Jobtitle) values (9,"Developer");
1 row created.
SQL>
SQL>
SQL> -- prepare data
SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (1, "Jason", to_date("19960725","YYYYMMDD"), 1234, 8767, "E", 2)
3 /
1 row created.
SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (2, "John", to_date("19970715","YYYYMMDD"), 2341, 3456, "W", 3)
3 /
1 row created.
SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (3, "Joe", to_date("19860125","YYYYMMDD"), 4321, 5654, "E", 3)
3 /
1 row created.
SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (4, "Tom", to_date("20060913","YYYYMMDD"), 2413, 6787, "W", 4)
3 /
1 row created.
SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (5, "Jane", to_date("20050417","YYYYMMDD"), 7654, 4345, "E", 4)
3 /
1 row created.
SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (6, "James", to_date("20040718","YYYYMMDD"), 5679, 6546, "W", 5)
3 /
1 row created.
SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (7, "Jodd", to_date("20030720","YYYYMMDD"), 5438, 7658, "E", 6)
3 /
1 row created.
SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION)
2 values (8, "Joke", to_date("20020101","YYYYMMDD"), 8765, 4543, "W")
3 /
1 row created.
SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION)
2 values (9, "Jack", to_date("20010829","YYYYMMDD"), 7896, 1232, "E")
3 /
1 row created.
SQL>
SQL>
SQL>
SQL> -- display data in the table
SQL> select * from Employee
2 /
EMPNO ENAME HIREDATE ORIG_SALARY CURR_SALARY R MANAGER_ID
---------- --------------- --------- ----------- ----------- - ----------
1 Jason 25-JUL-96 1234 8767 E 2
2 John 15-JUL-97 2341 3456 W 3
3 Joe 25-JAN-86 4321 5654 E 3
4 Tom 13-SEP-06 2413 6787 W 4
5 Jane 17-APR-05 7654 4345 E 4
6 James 18-JUL-04 5679 6546 W 5
7 Jodd 20-JUL-03 5438 7658 E 6
8 Joke 01-JAN-02 8765 4543 W
9 Jack 29-AUG-01 7896 1232 E
9 rows selected.
SQL> select * from job
2 /
EMPNO JOBTITLE
---------- --------------------
1 Tester
2 Accountant
3 Developer
4 COder
5 Director
6 Mediator
7 Proffessor
8 Programmer
9 Developer
9 rows selected.
SQL>
SQL> SELECT LEVEL, empno, manager_id, ename
2 FROM employee
3 START WITH empno = 1
4 CONNECT BY PRIOR empno = manager_id
5 ORDER BY LEVEL;
LEVEL EMPNO MANAGER_ID ENAME
---------- ---------- ---------- ---------------
1 1 2 Jason
SQL>
SQL> -- clean the table
SQL> drop table Employee
2 /
Table dropped.
SQL> drop table job
2 /
Table dropped.
SQL>
SQL>