Northwind2003 database

11 Aug 2014 11

Sakila database

11 Aug 2014 22

11 Aug 2014 3

MySQL server

Relational database management program Administer relational database Update database information Extract information through queries Server-client architecture User authentication

Competitors: Access, Oracle, PostgreSQL

3

11 Aug 2014 4

MySQL client

Personal program to access MySQL

Command line interface

HeidiSQL Preconfigured portable

version fromcourse website

4

11 Aug 2014 5

Starting HeidiSQL

1. Uncompress it on your Desktop2. Connect to alcor.inf.unibz.it3. Type your unibz username and password

To use it from outside unibz LAN, you need before to log in to VPN here https://vpn.scientificnet.org .

Manually configuring HeidiSQL (not needed) Installing MySQL server on your computer (useful but

not necessary)

5

11 Aug 2014 6

Using HeidiSQL Database structure in the left window Commands executed and errors in the log

window below Queries can be written in the Query tab

and executed pressing F9 or Highlighting some commands and pressing F1

activates the SQL help

6

11 Aug 2014 7

Using HeidiSQL USE {database}; or click in the left window You must have appropriate privileges:

GRANT SELECT GRANT INSERT GRANT UPDATE GRANT DELETE GRANT ALTER

No way to undo your changes!!! ROLLBACK; command does not work on most MySQL

tables

7

Selection query

11 Aug 2014 8

A question which produces a temporary table SELECT fields FROM table; SELECT fields FROM table WHERE condition

ORDER BY field ASC|DESC; Mathematical operations AND, OR, NOT and parentheses

Virtual field: expression AS name Views

CREATE VIEW name AS selection query; DROP VIEW name;

Selection query

11 Aug 2014 9

mathematical operators + - * / and comparisons = < > <= >= <> ROUND( ), ABS( ), EXP( ), SQRT( ), LOG( ) condition1 AND condition2, condition1 OR condition2, NOT condition field BETWEEN value1 AND value2 IS NULL, IS NOT NULL field IN (list) field LIKE expression containing % or _ CURDATE(), DATE_ADD(date, INTERVAL number DAY|MONTH|YEAR) YEAR(date), MONTH(date), DAY(date) DATEDIFF(date2,date1) To get difference in years:

Approximate: ROUND(DATEDIFF(date2,date1)/365.25) Exact: YEAR(date2) - YEAR(date1) - ( DATE_FORMAT( date2, '%m

%d' ) < DATE_FORMAT( date1, '%m%d' ) )

Joins

11 Aug 2014 10

Inner join SELECT fields FROM table1 INNER JOIN table2 ON

field1 = field2; Names containing spaces must be enclosed by

grave accent ` Values enclosed instead by apostrophe ’ Ambiguous field names use table.field

table AS shortname from now on you must use nickname

Difference between WHERE and ON Cross join Multiple inner joins

Summary query

11 Aug 2014 11

aggregates the records based on a GROUP BY instruction and returns one record per distinct value of GROUP BY fields

If no GROUP BY is inserted, it aggregates everything SELECT function(field), grouping fields FROM

tables with inner joins GROUP BY field; function is an aggregating function:

Sum(field), Avg(field), Max(field), Min(field) Count(*), Count(DISTINCT field)

Summary query

11 Aug 2014 12

Conditions WHERE condition filters (and is written)

before aggregation and thus must be used on fields which disappears after aggregation

HAVING condition filters (and is written) after aggregation and thus must be used on aggregating functions

fields which exist before and after aggregation, such as grouping fields, can be used in both conditions equivalently

Do not select extra fields in summary queries!

Modifying data

11 Aug 2014 13

Using HeidiSQL graphical interface TRUNCATE table; DELETE FROM table WHERE condition; UPDATE table SET field = value WHERE condition; INSERT INTO table (fields) VALUES (values), …, (values); Exporting text data

Fields’ delimiter Values’ encloser

Importing text data Prepare structure before

13

Field types

11 Aug 2014 14

INT -2 billions to 2 billions TINYINT 0 or 1 DECIMAL(total number of digits, number of decimal digits) FLOAT non-exact real number CHAR (number of characters) fixed length text VARCHAR(maximum number of characters) variable length text TEXT very long text up to 60,000 characters ENUM( value , … , value )

Pay attention to numbers DATE time is supposed to be midnight, DATETIME Options

NOT NULL, AUTO_INCREMENT, UNIQUE, DEFAULT default value, INDEX Primary key automatically has UNIQUE and NOT NULL and is an index

Numerical codes are not numbers!

Table

11 Aug 2014 15

CREATE TABLE table ( field field-type options, …, PRIMARY KEY (field), INDEX (field), CHECK (condition));

DROP TABLE table; ALTER TABLE table ADD field field-type options; ALTER TABLE table DROP field; ALTER TABLE table ADD PRIMARY KEY field; ALTER TABLE table DROP PRIMARY KEY; Using MySQL graphical interface

Steal code from another table

Create a blank database◦ Build the tables

Start from the tables on the “1” side Put appropriate types Put appropriate primary key

◦ Check the structure◦ Fill in the tables

16

Home exercise: Your library

Queries◦ Build a query to show book title, author surname,

publishing year and author birth date◦ Build a query to show book title, author surname and

publishing date only for German and French authors. Do not rewrite a new one. Modify easily the previous one

adding another field with a condition and hiding it◦ Build a query to show book title, author surname and

publishing date only for those book published before 1930. Do not rewrite a new one. Modify the first one.

17

Home exercise : Your library

Exercises◦ Is there the book TITLE?◦ Is there a book TITLE published after 1/1/2000?◦ Which books AUTHOR has published?

Improvements◦ Put NOT NULL for appropriate fields◦ Insert check constraints for appropriate fields◦ Build a structure for predefined values lists where

appropriate

18

Home exercise : Your library

Advanced queries. Build a query which:◦ shows book title, author surname and publishing year

only for those authors born before a date invented by you.

◦ shows book title, author surname and the age of the author when the book was published.

◦ counts the books for every author.◦ calculates the average publishing year of each author◦ calculates the average publishing year of each author

considering only German and English authors.

19

Home exercise : Your library

Build a blank database◦ Build the tables

Start from the tables on the “1” side Put appropriate types Put appropriate primary keys

◦ Check the structure◦ Fill in the tables

20

Home exercise : students and exams

Queries◦ Build a query which displays, for every

student, the list of his passed exams.◦ Build a query which displays the list of passed

exams and students’ last names, considering only who got a laude.

◦ Build a query which displays the student number (ordered from lowest to highest) of students who passed computer science.

21

Home exercise : students and exams

◦ Expand the database inserting information about professors and their exams Many to many relation another extra table

◦ Put NOT NULL for appropriate fields◦ Insert check constraints for appropriate fields◦ Build a structure for predefined values lists

where appropriate

22

Home exercise : students and exams

Advanced queries. Build a query which:◦ shows the list of courses of professor Coletti.◦ shows the list of exams of professor Coletti with the

average grade that students obtain in the exam (considering, obviously, only the passed attempts)

◦ shows the list of professor Coletti’s exams with the number of students who got more that 24

23

Home exercise : students and exams