Download International Computer Institute, Izmir, Turkey SQL, MySQL and PHP

International Computer Institute, Izmir, Turkey
SQL
Asst.Prof.Dr.İlker Kocabaş
UBİ502 at http://ube.ege.edu.tr/~ikocabas
Overview
 Joins: types and conditions
 Example 1: our languages
 relational algebra
 tuple relational calculus
 domain relational calculus
 SQL
 Examples 2, 3
 joins, aggregates, MySQL
 Join tricks
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.2 of 48
Modifications & additions by Cengiz Güngör
Schema Diagram for the Banking Enterprise
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.3 of 48
Modifications & additions by Cengiz Güngör
Joins
 Join types:
 Inner join
 Left outer join
 Right outer join
 Full outer join
 Join conditions:
 Natural
 On <predicate>
 Using (A1, …, An)
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.4 of 48
Modifications & additions by Cengiz Güngör
The loan and borrower Relations
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.5 of 48
Modifications & additions by Cengiz Güngör
loan INNER JOIN borrower
ON loan.loan-number = borrower.loan-number
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.6 of 48
Modifications & additions by Cengiz Güngör
loan LEFT OUTER JOIN borrower
USING (loan-number)
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.7 of 48
Modifications & additions by Cengiz Güngör
Join Conditions
 a INNER JOIN b USING (c1, ..., cn)
SELECT * FROM loan INNER JOIN borrower USING (loan_number);
+-------------+-------------+--------+---------------+-------------+
| loan_number | branch_name | amount | customer_name | loan_number |
+-------------+-------------+--------+---------------+-------------+
| L-16
| Perryridge |
1300 | Adams
| L-16
|
| L-93
| Mianus
|
500 | Curry
| L-93
|
...
| L-17
| Downtown
|
1000 | Williams
| L-17
|
+-------------+-------------+--------+---------------+-------------+
 Equivalent:
a INNER JOIN b ON (a.c1 = b.c1, …, a.cn = b.cn)
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.8 of 48
Modifications & additions by Cengiz Güngör
Join Conditions
 Suppose (c1, …, cn) is a complete list of attributes
common to A and B
 Then:
a INNER JOIN b USING (c1, …, cn)
is equivalent to:
a NATURAL JOIN b
 E.g. since there is only one common attribute
between loan and borrower, the following queries
give the same result:
SELECT * FROM loan INNER JOIN borrower
USING (loan_number);
SELECT * FROM loan NATURAL JOIN borrower;
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.9 of 48
Modifications & additions by Cengiz Güngör
Example 1: Our languages
Query: What branches are in Brooklyn?
branch-name (branch-city = “Brooklyn” (branch))
{t |  s branch (t[branch-name] = s[branch-name]
 s [branch-city] = “Brooklyn”)}
{ n  |  c, a ( n, c, a   branch  c = “Brooklyn”)}
SELECT branch-name FROM branch
WHERE branch_city = “Brooklyn”
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.10 of 48
Modifications & additions by Cengiz Güngör
Example 2
Who has a loan with a greater value than every loan at
Perryridge branch?
t1 ← mp(max) ( g max(amount) (branch-name = “Perryridge” (loan)))
(customer-name(loan-number(amount > t1.max (loan)) ⋈ borrower)
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.11 of 48
Modifications & additions by Cengiz Güngör
Example 2 (cont)
branch-name = “Perryridge” (loan)
mysql> SELECT * FROM loan
-> WHERE branch_name = "Perryridge";
+-------------+-------------+--------+
| loan_number | branch_name | amount |
+-------------+-------------+--------+
| L-15
| Perryridge
|
1500 |
| L-16
| Perryridge
|
1300 |
+-------------+-------------+--------+
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.12 of 48
Modifications & additions by Cengiz Güngör
Example 2 (cont)
g max(amount)
(branch-name = “Perryridge” (loan))
mysql> SELECT MAX(amount) FROM loan
-> WHERE branch_name = "Perryridge";
+-------------+
| max(amount) |
+-------------+
|
1500 |
+-------------+
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.13 of 48
Modifications & additions by Cengiz Güngör
Example 2 (cont)
mp(max) ( g max(amount) (branch-name = “Perryridge” (loan)))
mysql> SELECT MAX(amount) AS max FROM loan
-> WHERE branch_name = "Perryridge";
+------+
| max
|
+------+
| 1500 |
+------+
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.14 of 48
Modifications & additions by Cengiz Güngör
Example 2 (cont)
t1 ← mp(max) ( g max(amount) (branch-name = “Perryridge” (loan)))
mysql> CREATE TEMPORARY TABLE t1
-> SELECT MAX(amount) AS max FROM loan
-> WHERE branch_name = "Perryridge";
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.15 of 48
Modifications & additions by Cengiz Güngör
Example 2 (cont)
amount > t1.max (loan)
mysql> SELECT * FROM loan, t1
-> WHERE amount > t1.max;
+-------------+-------------+--------+------+
| loan_number | branch_name | amount | max
|
+-------------+-------------+--------+------+
| L-23
| Redwood
|
2000 | 1500 |
| L-20
| North Town
|
7500 | 1500 |
+-------------+-------------+--------+------+
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.16 of 48
Modifications & additions by Cengiz Güngör
Example 2 (cont)
(amount (amount > t1.max (loan))
mysql> SELECT amount FROM loan, t1
-> WHERE amount > t1.max;
+--------+
| amount |
+--------+
|
2000 |
|
7500 |
+--------+
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.17 of 48
Modifications & additions by Cengiz Güngör
Example 2 (cont)
customer-name(amount (amount > t1.max (loan)) ⋈ borrower)
mysql> SELECT customer_name
-> FROM loan NATURAL JOIN borrower, t1
-> WHERE amount > t1.max;
+---------------+
| customer_name |
+---------------+
| McBride
|
| Smith
|
+---------------+
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.18 of 48
Modifications & additions by Cengiz Güngör
Example 3
Query: What is the average loan amount held by customers in each
city?
branch-city
g avg(amount) (loan
⋈ branch)
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.19 of 48
Modifications & additions by Cengiz Güngör
Example 3 (cont)
mysql> select *
-> from loan natural join branch;
+-------------+-------------+--------+-------------+-------------+---------+
| loan_number | branch_name | amount | branch_name | branch_city | assets |
+-------------+-------------+--------+-------------+-------------+---------+
| L-17
| Downtown
|
1000 | Downtown
| Brooklyn
| 900000 |
| L-23
| Redwood
|
2000 | Redwood
| Palo Alto
| 2100000 |
| L-15
| Perryridge |
1500 | Perryridge | Horseneck
| 1700000 |
| L-14
| Downtown
|
1500 | Downtown
| Brooklyn
| 900000 |
| L-93
| Mianus
|
500 | Mianus
| Horseneck
| 400200 |
| L-11
| Round Hill |
900 | Round Hill | Horseneck
| 8000000 |
| L-16
| Perryridge |
1300 | Perryridge | Horseneck
| 1700000 |
| L-20
| North Town |
7500 | North Town | Rye
| 3700000 |
| L-21
| Central
|
570 | Central
| Rye
| 400280 |
+-------------+-------------+--------+-------------+-------------+---------+
 Would like to see just the branch_name and branch_city columns
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.20 of 48
Modifications & additions by Cengiz Güngör
Example 3 (cont)
mysql> select branch_city, amount
-> from loan natural join branch;
+-------------+--------+
| branch_city | amount |
+-------------+--------+
| Brooklyn
|
1000 |
| Palo Alto
|
2000 |
| Horseneck
|
1500 |
| Brooklyn
|
1500 |
| Horseneck
|
500 |
| Horseneck
|
900 |
| Horseneck
|
1300 |
| Rye
|
7500 |
| Rye
|
570 |
+-------------+--------+
 Would like to see this table sorted by branch_city
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.21 of 48
Modifications & additions by Cengiz Güngör
Example 3 (cont)
mysql> select branch_city, amount
-> from loan natural join branch
-> order by branch_city;
+-------------+--------+
| branch_city | amount |
+-------------+--------+
| Brooklyn
|
1000 |
| Brooklyn
|
1500 |
| Horseneck
|
1300 |
| Horseneck
|
1500 |
| Horseneck
|
500 |
| Horseneck
|
900 |
| Palo Alto
|
2000 |
| Rye
|
7500 |
| Rye
|
570 |
+-------------+--------+
 Next: compute average for each group
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.22 of 48
Modifications & additions by Cengiz Güngör
Example 3 (cont)
mysql> select branch_city, avg(amount)
-> from loan natural join branch
-> group by branch_city;
+-------------+-------------+
| branch_city | avg(amount) |
+-------------+-------------+
| Brooklyn
|
1250.0000 |
| Horseneck
|
1050.0000 |
| Palo Alto
|
2000.0000 |
| Rye
|
4035.0000 |
+-------------+-------------+
 Suppose we wanted to impose a constraint on the result – use a
HAVING clause
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.23 of 48
Modifications & additions by Cengiz Güngör
Example 3 (cont)
mysql> select branch_city as city, avg(amount) as average
-> from loan natural join branch
-> group by branch_city
-> having (avg(amount) > 1500);
+-----------+-----------+
| city
| average
|
+-----------+-----------+
| Palo Alto | 2000.0000 |
| Rye
| 4035.0000 |
+-----------+-----------+
 Note: we also renamed the columns
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.24 of 48
Modifications & additions by Cengiz Güngör
Join tricks
 Restrict a to just those rows compatible with b
 SELECT DISTINCT a.* FROM a NATURAL JOIN b;
 E.g. list tuples from the borrower table only for those borrowers
who are depositors:
 SELECT DISTINCT borrower.*
FROM borrower NATURAL JOIN depositor;
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.25 of 48
Modifications & additions by Cengiz Güngör
Join tricks (cont)
 Compute set difference without using EXCEPT
(MySQL 3.23 doesn’t have set operations)
i.e.remove from a those tuples compatible with b
 SELECT DISTINCT a.* FROM a NATURAL LEFT OUTER JOIN b
WHERE b.x is NULL
 E.g. list those tuples from the borrower table only for those
borrowers who are not depositors:
 SELECT DISTINCT borrower.*
FROM borrower NATURAL LEFT OUTER JOIN depositor
WHERE depositor.customer_name is NULLS
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.26 of 48
Modifications & additions by Cengiz Güngör
Review
 A NATURAL JOIN uses common column headings, and it is not
possible to attach an ON or USING clause
 An INNER JOIN results in a table where each tuple is a
combination of information from both argument tables
 An OUTER JOIN is an INNER JOIN padded with additional
tuples
 The ON clause lists common attributes which must be equal on
both sides of the join
 The USING clause permits us to enforce equality between
attributes having different names, e.g. ON a.x = b.y
 It also permits us to use inequalities, e.g. ON a.x > b.y
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.27 of 48
Modifications & additions by Cengiz Güngör
PS: Theta Join
A ⋈C B ≝ C (A ⋈ B)
 For notational convenience, we permit ourselves to write a select
condition on the join operator
 This is called “theta join” because the condition is sometimes
represented as a theta subscript:
⋈θ
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.28 of 48
Modifications & additions by Cengiz Güngör
READING
MySQL manual chapter 3:
Tutorial Introduction
http://www.mysql.com/documentation/mysql/
bychapter/manual_Tutorial.html
UBI 502
Database Management Systems
©Silberschatz, Korth and Sudarshan
5.29 of 48
Modifications & additions by Cengiz Güngör