Oracle PL/SQL Tutorial/Query Select/Nested Subquery
Версия от 13:45, 26 мая 2010; (обсуждение)
Содержание
How to have the subquery select from a different table than the parent statement
SQL> --
SQL>
SQL>
SQL> CREATE TABLE product_order (
2 product_name VARCHAR2(25),
3 salesperson VARCHAR2(3),
4 order_date DATE,
5 quantity NUMBER(4,2)
6 );
Table created.
SQL>
SQL> CREATE TABLE person (
2 person_code VARCHAR2(3) PRIMARY KEY,
3 first_name VARCHAR2(15),
4 last_name VARCHAR2(20),
5 hire_date DATE
6 );
Table created.
SQL>
SQL>
SQL> INSERT INTO person VALUES ("CA", "Chase", "At", "01-FEB-02");
1 row created.
SQL> INSERT INTO person VALUES ("GA", "Gary", "Talor", "15-FEB-02");
1 row created.
SQL> INSERT INTO person VALUES ("BB", "Bob", "Bark", "28-FEB-02");
1 row created.
SQL> INSERT INTO person VALUES ("LB", "Laren", "Baby", "01-MAR-02");
1 row created.
SQL> INSERT INTO person VALUES ("LN", "Linda", "Norman","01-JUN-03");
1 row created.
SQL>
SQL>
SQL> INSERT INTO product_order VALUES ("Product 1", "CA", "14-JUL-03", 1);
1 row created.
SQL> INSERT INTO product_order VALUES ("Product 2", "BB", "14-JUL-03", 75);
1 row created.
SQL> INSERT INTO product_order VALUES ("Product 3", "GA", "14-JUL-03", 2);
1 row created.
SQL> INSERT INTO product_order VALUES ("Product 4", "GA", "15-JUL-03", 8);
1 row created.
SQL> INSERT INTO product_order VALUES ("Product 5", "LB", "15-JUL-03", 20);
1 row created.
SQL> INSERT INTO product_order VALUES ("Product 6", "CA", "16-JUL-03", 5);
1 row created.
SQL> INSERT INTO product_order VALUES ("Product 7", "CA", "17-JUL-03", 1);
1 row created.
SQL>
SQL>
SQL> SELECT * FROM product_order
2 WHERE salesperson = (
3 SELECT person_code
4 FROM person
5 WHERE first_name = "Gary" AND last_name = "Anderson"
6 );
no rows selected
SQL>
SQL> drop table product_order;
Table dropped.
SQL> drop table person;
Table dropped.
Join a subquery
SQL>
SQL>
SQL> create table employees(
2 empno NUMBER(4)
3 , ename VARCHAR2(8)
4 , init VARCHAR2(5)
5 , job VARCHAR2(8)
6 , mgr NUMBER(4)
7 , bdate DATE
8 , msal NUMBER(6,2)
9 , comm NUMBER(6,2)
10 , deptno NUMBER(2) ) ;
Table created.
SQL>
SQL>
SQL> insert into employees values(1,"Jason", "N", "TRAINER", 2, date "1965-12-18", 800 , NULL, 10);
1 row created.
SQL> insert into employees values(2,"Jerry", "J", "SALESREP",3, date "1966-11-19", 1600, 300, 10);
1 row created.
SQL> insert into employees values(3,"Jord", "T" , "SALESREP",4, date "1967-10-21", 1700, 500, 20);
1 row created.
SQL> insert into employees values(4,"Mary", "J", "MANAGER", 5, date "1968-09-22", 1800, NULL, 20);
1 row created.
SQL> insert into employees values(5,"Joe", "P", "SALESREP",6, date "1969-08-23", 1900, 1400, 30);
1 row created.
SQL> insert into employees values(6,"Black", "R", "MANAGER", 7, date "1970-07-24", 2000, NULL, 30);
1 row created.
SQL> insert into employees values(7,"Red", "A", "MANAGER", 8, date "1971-06-25", 2100, NULL, 40);
1 row created.
SQL> insert into employees values(8,"White", "S", "TRAINER", 9, date "1972-05-26", 2200, NULL, 40);
1 row created.
SQL> insert into employees values(9,"Yellow", "C", "DIRECTOR",10, date "1973-04-27", 2300, NULL, 20);
1 row created.
SQL> insert into employees values(10,"Pink", "J", "SALESREP",null,date "1974-03-28", 2400, 0, 30);
1 row created.
SQL>
SQL>
SQL> select e.ename, e.init, e.msal
2 from employees e
3 join
4 (select x.deptno
5 , avg(x.msal) avg_sal
6 from employees x
7 group by x.deptno ) g
8 using (deptno)
9 where e.msal > g.avg_sal;
last_name INIT MSAL
-------------------- ----- ------
Pink J 2400
Yellow C 2300
White S 2200
Jerry J 1600
4 rows selected.
SQL>
SQL>
SQL> drop table employees;
Table dropped.
SQL>
SQL>
Subquery as a column
SQL>
SQL>
SQL> create table departments
2 ( deptno NUMBER(2)
3 , dname VARCHAR2(10)
4 , location VARCHAR2(20)
5 , mgr NUMBER(4)
6 ) ;
Table created.
SQL>
SQL> insert into departments values (10,"ACCOUNTING","NEW YORK" , 2);
1 row created.
SQL> insert into departments values (20,"TRAINING", "VANCOUVER", 3);
1 row created.
SQL> insert into departments values (30,"SALES", "CHICAGO", 4);
1 row created.
SQL> insert into departments values (40,"HR", "BOSTON", 5);
1 row created.
SQL>
SQL>
SQL> create table employees(
2 empno NUMBER(4)
3 , ename VARCHAR2(8)
4 , init VARCHAR2(5)
5 , job VARCHAR2(8)
6 , mgr NUMBER(4)
7 , bdate DATE
8 , msal NUMBER(6,2)
9 , comm NUMBER(6,2)
10 , deptno NUMBER(2) ) ;
Table created.
SQL>
SQL>
SQL> insert into employees values(1,"Jason", "N", "TRAINER", 2, date "1965-12-18", 800 , NULL, 10);
1 row created.
SQL> insert into employees values(2,"Jerry", "J", "SALESREP",3, date "1966-11-19", 1600, 300, 10);
1 row created.
SQL> insert into employees values(3,"Jord", "T" , "SALESREP",4, date "1967-10-21", 1700, 500, 20);
1 row created.
SQL> insert into employees values(4,"Mary", "J", "MANAGER", 5, date "1968-09-22", 1800, NULL, 20);
1 row created.
SQL> insert into employees values(5,"Joe", "P", "SALESREP",6, date "1969-08-23", 1900, 1400, 30);
1 row created.
SQL> insert into employees values(6,"Black", "R", "MANAGER", 7, date "1970-07-24", 2000, NULL, 30);
1 row created.
SQL> insert into employees values(7,"Red", "A", "MANAGER", 8, date "1971-06-25", 2100, NULL, 40);
1 row created.
SQL> insert into employees values(8,"White", "S", "TRAINER", 9, date "1972-05-26", 2200, NULL, 40);
1 row created.
SQL> insert into employees values(9,"Yellow", "C", "DIRECTOR",10, date "1973-04-27", 2300, NULL, 20);
1 row created.
SQL> insert into employees values(10,"Pink", "J", "SALESREP",null,date "1974-03-28", 2400, 0, 30);
1 row created.
SQL>
SQL>
SQL>
SQL>
SQL> select d.deptno, d.dname, d.location
2 , (select count(*)
3 from employees e
4 where e.deptno = d.deptno) as emp_count
5 from departments d;
DEPTNO DNAME LOCATION EMP_COUNT
------ ---------- -------------------- ---------
10 ACCOUNTING NEW YORK 2
20 TRAINING VANCOUVER 3
30 SALES CHICAGO 3
40 HR BOSTON 2
4 rows selected.
SQL>
SQL> drop table employees;
Table dropped.
SQL>
SQL> drop table departments;
Table dropped.
SQL>
SQL>
Writing Nested Subqueries
Nest subqueries inside other subqueries can be 255-level depth.
SQL> -- create demo table
SQL> create table Employee(
2 ID VARCHAR2(4 BYTE) NOT NULL,
3 First_Name VARCHAR2(10 BYTE),
4 Last_Name VARCHAR2(10 BYTE),
5 Start_Date DATE,
6 End_Date DATE,
7 Salary Number(8,2),
8 City VARCHAR2(10 BYTE),
9 Description VARCHAR2(15 BYTE)
10 )
11 /
Table created.
SQL>
SQL> -- prepare data
SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values ("01","Jason", "Martin", to_date("19960725","YYYYMMDD"), to_date("20060725","YYYYMMDD"), 1234.56, "Toronto", "Programmer")
3 /
1 row created.
SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("02","Alison", "Mathews", to_date("19760321","YYYYMMDD"), to_date("19860221","YYYYMMDD"), 6661.78, "Vancouver","Tester")
3 /
1 row created.
SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("03","James", "Smith", to_date("19781212","YYYYMMDD"), to_date("19900315","YYYYMMDD"), 6544.78, "Vancouver","Tester")
3 /
1 row created.
SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("04","Celia", "Rice", to_date("19821024","YYYYMMDD"), to_date("19990421","YYYYMMDD"), 2344.78, "Vancouver","Manager")
3 /
1 row created.
SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("05","Robert", "Black", to_date("19840115","YYYYMMDD"), to_date("19980808","YYYYMMDD"), 2334.78, "Vancouver","Tester")
3 /
1 row created.
SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("06","Linda", "Green", to_date("19870730","YYYYMMDD"), to_date("19960104","YYYYMMDD"), 4322.78,"New York", "Tester")
3 /
1 row created.
SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("07","David", "Larry", to_date("19901231","YYYYMMDD"), to_date("19980212","YYYYMMDD"), 7897.78,"New York", "Manager")
3 /
1 row created.
SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("08","James", "Cat", to_date("19960917","YYYYMMDD"), to_date("20020415","YYYYMMDD"), 1232.78,"Vancouver", "Tester")
3 /
1 row created.
SQL>
SQL>
SQL>
SQL> -- display data in the table
SQL> select * from Employee
2 /
ID FIRST_NAME LAST_NAME START_DAT END_DATE SALARY CITY DESCRIPTION
---- ---------- ---------- --------- --------- ---------- ---------- ---------------
01 Jason Martin 25-JUL-96 25-JUL-06 1234.56 Toronto Programmer
02 Alison Mathews 21-MAR-76 21-FEB-86 6661.78 Vancouver Tester
03 James Smith 12-DEC-78 15-MAR-90 6544.78 Vancouver Tester
04 Celia Rice 24-OCT-82 21-APR-99 2344.78 Vancouver Manager
05 Robert Black 15-JAN-84 08-AUG-98 2334.78 Vancouver Tester
06 Linda Green 30-JUL-87 04-JAN-96 4322.78 New York Tester
07 David Larry 31-DEC-90 12-FEB-98 7897.78 New York Manager
08 James Cat 17-SEP-96 15-APR-02 1232.78 Vancouver Tester
8 rows selected.
SQL>
SQL>
SQL> SELECT city, AVG(salary)
2 FROM employee
3 GROUP BY city
4 HAVING AVG(salary) <
5 (SELECT MAX(AVG(salary))
6 FROM employee
7 WHERE id IN
8 (SELECT id
9 FROM employee
10 WHERE city = "Vancouver")
11 GROUP BY city);
CITY AVG(SALARY)
---------- -----------
Toronto 1234.56
SQL>
SQL>
SQL>
SQL> -- clean the table
SQL> drop table Employee
2 /
Table dropped.
SQL>