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33>
34> CREATE TABLE works_on (emp_no INTEGER NOT NULL,
35> project_no CHAR(4) NOT NULL,
36> job CHAR (15) NULL,
37> enter_date DATETIME NULL)
38>
39> insert into works_on values (1, 'p1', 'analyst', '1997.10.1')
40> insert into works_on values (1, 'p3', 'manager', '1999.1.1')
41> insert into works_on values (2, 'p2', 'clerk', '1998.2.15')
42> insert into works_on values (2, 'p2', NULL, '1998.6.1')
43> insert into works_on values (3, 'p2', NULL, '1997.12.15')
44> insert into works_on values (4, 'p3', 'analyst', '1998.10.15')
45> insert into works_on values (5, 'p1', 'manager', '1998.4.15')
46> insert into works_on values (6, 'p1', NULL, '1998.8.1')
47> insert into works_on values (7, 'p2', 'clerk', '1999.2.1')
48> insert into works_on values (8, 'p3', 'clerk', '1997.11.15')
49> insert into works_on values (7, 'p1', 'clerk', '1998.1.4')
50>
51> select * from works_on
52> 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> CREATE TABLE employee (emp_no INTEGER NOT NULL,
3> emp_fname CHAR(20) NOT NULL,
4> emp_lname CHAR(20) NOT NULL,
5> dept_no CHAR(4) NULL)
6>
7> insert into employee values(1, 'Matthew', 'Smith', 'd3')
8> insert into employee values(2, 'Ann', 'Jones', 'd3')
9> insert into employee values(3, 'John', 'Barrimore','d1')
10> insert into employee values(4, 'James', 'James', 'd2')
11> insert into employee values(5, 'Elsa', 'Bertoni', 'd2')
12> insert into employee values(6, 'Elke', 'Hansel', 'd2')
13> insert into employee values(7, 'Sybill', 'Moser', 'd1')
14>
15> select * from employee
16> 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> -- Join Advantages
3>
4> -- Joins are advantageous over subqueries if the SELECT list in a query contains columns from more than one table
5>
6> SELECT employee.emp_no, emp_lname, job
7> FROM employee, works_on
8> WHERE employee.emp_no = works_on.emp_no
9> AND enter_date = '10.15.1998'
10> GO
emp_no emp_lname job
----------- -------------------- ---------------
4 James analyst
(1 rows affected)
1>
2> drop table employee
3> drop table works_on
4> GO
1>
2>
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