SQL Server/T-SQL/Subquery/Nested Subquery

Subqueries can be nested

1>
2> create table employee(
3>     ID          int,
4>     name        nvarchar (10),
5>     salary      int )
6> 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> -- Subqueries can be nested.
4>
5> SELECT ID, Name
6> FROM Employee
7> WHERE ID IN
8>       ( SELECT ID
9>         FROM Job
10>         WHERE title IN
11>             (  SELECT title
12>                FROM job )
13>       )
14> GO
ID          Name
----------- ----------
          1 Jason
          2 Robert
          3 Celia
          4 Linda
(4 rows affected)
1>
2> drop table employee;
3> drop table job;
4> GO
1>
2>

Using a Nested Subquery

 

4> CREATE TABLE employee(
5>    id          INTEGER NOT NULL PRIMARY KEY,
6>    first_name  VARCHAR(10),
7>    last_name   VARCHAR(10),
8>    salary      DECIMAL(10,2),
9>    start_Date  DATETIME,
10>    region      VARCHAR(10),
11>    city        VARCHAR(20),
12>    managerid   INTEGER
13> );
14> GO
1> INSERT INTO employee VALUES (1, "Jason" ,  "Martin", 5890,"2005-03-22","North","Vancouver",3);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (2, "Alison",  "Mathews",4789,"2003-07-21","South","Utown",4);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (3, "James" ,  "Smith",  6678,"2001-12-01","North","Paris",5);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (4, "Celia" ,  "Rice",   5567,"2006-03-03","South","London",6);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (5, "Robert",  "Black",  4467,"2004-07-02","East","Newton",7);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (6, "Linda" ,  "Green" , 6456,"2002-05-19","East","Calgary",8);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (7, "David" ,  "Larry",  5345,"2008-03-18","West","New York",9);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (8, "James" ,  "Cat",    4234,"2007-07-17","West","Regina",9);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (9, "Joan"  ,  "Act",    6123,"2001-04-16","North","Toronto",10);
2> GO
(1 rows affected)
1>
2> select * from employee;
3> GO
id          first_name last_name  salary       start_Date              region     city                 managerid
----------- ---------- ---------- ------------ ----------------------- ---------- -------------------- -----------
          1 Jason      Martin          5890.00 2005-03-22 00:00:00.000 North      Vancouver                      3
          2 Alison     Mathews         4789.00 2003-07-21 00:00:00.000 South      Utown                          4
          3 James      Smith           6678.00 2001-12-01 00:00:00.000 North      Paris                          5
          4 Celia      Rice            5567.00 2006-03-03 00:00:00.000 South      London                         6
          5 Robert     Black           4467.00 2004-07-02 00:00:00.000 East       Newton                         7
          6 Linda      Green           6456.00 2002-05-19 00:00:00.000 East       Calgary                        8
          7 David      Larry           5345.00 2008-03-18 00:00:00.000 West       New York                       9
          8 James      Cat             4234.00 2007-07-17 00:00:00.000 West       Regina                         9
          9 Joan       Act             6123.00 2001-04-16 00:00:00.000 North      Toronto                       10
(9 rows affected)
1>
2>
3>
4> 
5> SELECT
6>   MIN (Start_Date),
7>   (SELECT MAX (Start_Date) FROM Employee)
8> FROM
9>   Employee
10>
11>
12>
13>
14> drop table employee;
15> GO
----------------------- -----------------------
2001-04-16 00:00:00.000 2008-03-18 00:00:00.000
(1 rows affected)