SQL Server/T-SQL/Subquery/Correlated subquery
Содержание
- 1 Correlated subquery: the inner query depends on the outer query for any of its values
- 2 Correlated subquery using Distinct
- 3 Correlated subquery using the department table in both inner and outer queries
- 4 Leaf-Level Employees (Employees with No Subordinates), Correlated Subquery Syntax
- 5 Leaf-Level Employees (Employees with No Subordinates), Join Syntax
- 6 WHERE clause in the subquery"s SELECT statement links the inner query to the outer query
1> CREATE TABLE employee (emp_no INTEGER NOT NULL,
2> emp_fname CHAR(20) NOT NULL,
3> emp_lname CHAR(20) NOT NULL,
4> dept_no CHAR(4) NULL)
5>
6> insert into employee values(1, "Matthew", "Smith", "d3")
7> insert into employee values(2, "Ann", "Jones", "d3")
8> insert into employee values(3, "John", "Barrimore","d1")
9> insert into employee values(4, "James", "James", "d2")
10> insert into employee values(5, "Elsa", "Bertoni", "d2")
11> insert into employee values(6, "Elke", "Hansel", "d2")
12> insert into employee values(7, "Sybill", "Moser", "d1")
13>
14> select * from employee
15> GO
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
emp_no emp_fname emp_lname dept_no
----------- -------------------- -------------------- -------
1 Matthew Smith d3
2 Ann Jones d3
3 John Barrimore d1
4 James James d2
5 Elsa Bertoni d2
6 Elke Hansel d2
7 Sybill Moser d1
(7 rows affected)
1>
2> CREATE TABLE works_on (emp_no INTEGER NOT NULL,
3> project_no CHAR(4) NOT NULL,
4> job CHAR (15) NULL,
5> enter_date DATETIME NULL)
6>
7> insert into works_on values (1, "p1", "analyst", "1997.10.1")
8> insert into works_on values (1, "p3", "manager", "1999.1.1")
9> insert into works_on values (2, "p2", "clerk", "1998.2.15")
10> insert into works_on values (2, "p2", NULL, "1998.6.1")
11> insert into works_on values (3, "p2", NULL, "1997.12.15")
12> insert into works_on values (4, "p3", "analyst", "1998.10.15")
13> insert into works_on values (5, "p1", "manager", "1998.4.15")
14> insert into works_on values (6, "p1", NULL, "1998.8.1")
15> insert into works_on values (7, "p2", "clerk", "1999.2.1")
16> insert into works_on values (8, "p3", "clerk", "1997.11.15")
17> insert into works_on values (7, "p1", "clerk", "1998.1.4")
18>
19> select * from works_on
20> GO
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
emp_no project_no job enter_date
----------- ---------- --------------- -----------------------
1 p1 analyst 1997-10-01 00:00:00.000
1 p3 manager 1999-01-01 00:00:00.000
2 p2 clerk 1998-02-15 00:00:00.000
2 p2 NULL 1998-06-01 00:00:00.000
3 p2 NULL 1997-12-15 00:00:00.000
4 p3 analyst 1998-10-15 00:00:00.000
5 p1 manager 1998-04-15 00:00:00.000
6 p1 NULL 1998-08-01 00:00:00.000
7 p2 clerk 1999-02-01 00:00:00.000
8 p3 clerk 1997-11-15 00:00:00.000
7 p1 clerk 1998-01-04 00:00:00.000
(11 rows affected)
1>
2>
3> -- Correlated Subqueries
4>
5> -- A subquery is said to be a correlated subquery if the inner query depends on the outer query for any of its values.
6>
7> SELECT emp_lname
8> FROM employee
9> WHERE emp_no IN
10> (SELECT emp_no
11> FROM works_on
12> WHERE project_no="p3")
13> GO
emp_lname
--------------------
Smith
James
(2 rows affected)
1>
2> drop table works_on
3> drop table employee
4> GO
1>
1> create table employee(
2> ID int,
3> name nvarchar (10),
4> salary int )
5> GO
1>
2> create table job(
3> ID int,
4> title nvarchar (10),
5> averageSalary int)
6> GO
1>
2>
3> insert into employee (ID, name, salary) values (1, "Jason", 1234)
4> GO
(1 rows affected)
1> insert into employee (ID, name, salary) values (2, "Robert", 4321)
2> GO
(1 rows affected)
1> insert into employee (ID, name, salary) values (3, "Celia", 5432)
2> GO
(1 rows affected)
1> insert into employee (ID, name, salary) values (4, "Linda", 3456)
2> GO
(1 rows affected)
1> insert into employee (ID, name, salary) values (5, "David", 7654)
2> GO
(1 rows affected)
1> insert into employee (ID, name, salary) values (6, "James", 4567)
2> GO
(1 rows affected)
1> insert into employee (ID, name, salary) values (7, "Alison", 8744)
2> GO
(1 rows affected)
1> insert into employee (ID, name, salary) values (8, "Chris", 9875)
2> GO
(1 rows affected)
1> insert into employee (ID, name, salary) values (9, "Mary", 2345)
2> GO
(1 rows affected)
1>
2> insert into job(ID, title, averageSalary) values(1,"Developer",3000)
3> GO
(1 rows affected)
1> insert into job(ID, title, averageSalary) values(2,"Tester", 4000)
2> GO
(1 rows affected)
1> insert into job(ID, title, averageSalary) values(3,"Designer", 5000)
2> GO
(1 rows affected)
1> insert into job(ID, title, averageSalary) values(4,"Programmer", 6000)
2> GO
(1 rows affected)
1>
2>
3> select * from employee;
4> GO
ID name salary
----------- ---------- -----------
1 Jason 1234
2 Robert 4321
3 Celia 5432
4 Linda 3456
5 David 7654
6 James 4567
7 Alison 8744
8 Chris 9875
9 Mary 2345
(9 rows affected)
1> select * from job;
2> GO
ID title averageSalary
----------- ---------- -------------
1 Developer 3000
2 Tester 4000
3 Designer 5000
4 Programmer 6000
(4 rows affected)
1>
2>
3> -- Correlated subquery using Distinct:
4> SELECT ID
5> , Name
6> FROM Employee AS e
7> WHERE 1 =
8> (SELECT DISTINCT ID
9> FROM Job As j
10> WHERE j.ID = e.ID)
11>
12>
13>
14> drop table employee;
15> drop table job;
16> GO
ID Name
----------- ----------
1 Jason
(1 rows affected)
1>
2>
1>
2> CREATE TABLE department(dept_no CHAR(4) NOT NULL,
3> dept_name CHAR(25) NOT NULL,
4> location CHAR(30) NULL)
5>
6> insert into department values ("d1", "developer", "Dallas")
7> insert into department values ("d2", "tester", "Seattle")
8> insert into department values ("d3", "marketing", "Dallas")
9>
10> select * from department
11> GO
(1 rows affected)
(1 rows affected)
(1 rows affected)
dept_no dept_name location
------- ------------------------- ------------------------------
d1 developer Dallas
d2 tester Seattle
d3 marketing Dallas
(3 rows affected)
1> -- Correlated subquery using the department table in both inner and outer queries
2>
3> SELECT t1.*
4> FROM department t1
5> WHERE t1.location IN
6> (SELECT t2.location
7> FROM department t2
8> WHERE t1.dept_no <> t2.dept_no)
9> GO
dept_no dept_name location
------- ------------------------- ------------------------------
d1 developer Dallas
d3 marketing Dallas
(2 rows affected)
1>
2> drop table department
3> GO
1>
5>
6>
7>
8> CREATE TABLE Employees
9> (
10> empid int NOT NULL,
11> mgrid int NULL,
12> empname varchar(25) NOT NULL,
13> salary money NOT NULL)
14> GO
1> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(1, NULL, "Nancy", $10000.00)
2> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(2, 1, "Andrew", $5000.00)
3> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(3, 1, "Janet", $5000.00)
4> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(4, 1, "Margaret", $5000.00)
5> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(5, 2, "Steven", $2500.00)
6> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(6, 2, "Michael", $2500.00)
7> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(7, 3, "Robert", $2500.00)
8> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(8, 3, "Laura", $2500.00)
9> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(9, 3, "Ann", $2500.00)
10> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(10, 4, "Ina", $2500.00)
11> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(11, 7, "David", $2000.00)
12> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(12, 7, "Ron", $2000.00)
13> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(13, 7, "Dan", $2000.00)
14> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(14, 11, "James", $1500.00)
15>
16>
17> SELECT *
18> FROM
19> Employees AS M
20> WHERE
21> NOT EXISTS
22> (
23> SELECT
24> empid
25> FROM
26> Employees AS E
27> WHERE
28> E.mgrid = M.empid
29> )
30> GO
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
empid mgrid empname salary
----------- ----------- ------------------------- ---------------------
5 2 Steven 2500.0000
6 2 Michael 2500.0000
8 3 Laura 2500.0000
9 3 Ann 2500.0000
10 4 Ina 2500.0000
12 7 Ron 2000.0000
13 7 Dan 2000.0000
14 11 James 1500.0000
(8 rows affected)
1>
2>
3> drop table Employees;
4> GO
Leaf-Level Employees (Employees with No Subordinates), Join Syntax
3>
4>
5>
6> CREATE TABLE Employees
7> (
8> empid int NOT NULL,
9> mgrid int NULL,
10> empname varchar(25) NOT NULL,
11> salary money NOT NULL)
12> GO
1> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(1, NULL, "Nancy", $10000.00)
2> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(2, 1, "Andrew", $5000.00)
3> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(3, 1, "Janet", $5000.00)
4> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(4, 1, "Margaret", $5000.00)
5> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(5, 2, "Steven", $2500.00)
6> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(6, 2, "Michael", $2500.00)
7> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(7, 3, "Robert", $2500.00)
8> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(8, 3, "Laura", $2500.00)
9> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(9, 3, "Ann", $2500.00)
10> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(10, 4, "Ina", $2500.00)
11> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(11, 7, "David", $2000.00)
12> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(12, 7, "Ron", $2000.00)
13> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(13, 7, "Dan", $2000.00)
14> INSERT INTO employees(empid, mgrid, empname, salary) VALUES(14, 11, "James", $1500.00)
15>
16>
17> SELECT
18> M.*
19> FROM
20> Employees AS M
21> LEFT OUTER JOIN
22> Employees AS E ON M.empid = E.mgrid
23> WHERE
24> E.mgrid IS NULL
25> GO
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
empid mgrid empname salary
----------- ----------- ------------------------- ---------------------
5 2 Steven 2500.0000
6 2 Michael 2500.0000
8 3 Laura 2500.0000
9 3 Ann 2500.0000
10 4 Ina 2500.0000
12 7 Ron 2000.0000
13 7 Dan 2000.0000
14 11 James 1500.0000
(8 rows affected)
1>
2>
3> drop table Employees;
4> GO
1>
WHERE clause in the subquery"s SELECT statement links the inner query to the outer query
1> create table employee(
2> ID int,
3> name nvarchar (10),
4> salary int )
5> GO
1>
2> create table job(
3> ID int,
4> title nvarchar (10),
5> averageSalary int)
6> GO
1>
2>
3> insert into employee (ID, name, salary) values (1, "Jason", 1234)
4> GO
(1 rows affected)
1> insert into employee (ID, name, salary) values (2, "Robert", 4321)
2> GO
(1 rows affected)
1> insert into employee (ID, name, salary) values (3, "Celia", 5432)
2> GO
(1 rows affected)
1> insert into employee (ID, name, salary) values (4, "Linda", 3456)
2> GO
(1 rows affected)
1> insert into employee (ID, name, salary) values (5, "David", 7654)
2> GO
(1 rows affected)
1> insert into employee (ID, name, salary) values (6, "James", 4567)
2> GO
(1 rows affected)
1> insert into employee (ID, name, salary) values (7, "Alison", 8744)
2> GO
(1 rows affected)
1> insert into employee (ID, name, salary) values (8, "Chris", 9875)
2> GO
(1 rows affected)
1> insert into employee (ID, name, salary) values (9, "Mary", 2345)
2> GO
(1 rows affected)
1>
2> insert into job(ID, title, averageSalary) values(1,"Developer",3000)
3> GO
(1 rows affected)
1> insert into job(ID, title, averageSalary) values(2,"Tester", 4000)
2> GO
(1 rows affected)
1> insert into job(ID, title, averageSalary) values(3,"Designer", 5000)
2> GO
(1 rows affected)
1> insert into job(ID, title, averageSalary) values(4,"Programmer", 6000)
2> GO
(1 rows affected)
1>
2>
3> select * from employee;
4> GO
ID name salary
----------- ---------- -----------
1 Jason 1234
2 Robert 4321
3 Celia 5432
4 Linda 3456
5 David 7654
6 James 4567
7 Alison 8744
8 Chris 9875
9 Mary 2345
(9 rows affected)
1> select * from job;
2> GO
ID title averageSalary
----------- ---------- -------------
1 Developer 3000
2 Tester 4000
3 Designer 5000
4 Programmer 6000
(4 rows affected)
1>
2>
3> -- The WHERE clause in the subquery"s SELECT statement links the inner query to the outer query.
4> -- This makes the inner query a correlated subquery
5>
6> SELECT TOP 29 e.ID, e.name, (SELECT j.title FROM job j WHERE j.ID = e.ID) "title"
7> FROM Employee e
8> GO
ID name title
----------- ---------- ----------
1 Jason Developer
2 Robert Tester
3 Celia Designer
4 Linda Programmer
5 David NULL
6 James NULL
7 Alison NULL
8 Chris NULL
9 Mary NULL
(9 rows affected)
1>
2> drop table employee;
3> drop table job;
4> GO
1>