TUSQL

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Structured Query Language

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SQL lowdown

• Used by Relational Database Management Systems (RDBMS)

• Used to create and alter a DB

• Used to query a DB

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RDBMS quick l👀k

• The standard for DBs these days

• Based on relations

• Tables are related via common fields (FK = PK)

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Relations are modeled with tables

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Tables a.k.a Entities

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The schema ...

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Course

Field Details

id INT(11) NOT NULL AUTO_INCREMENT

number VARCHAR(10) NOT NULL

title VARCHAR(50) DEFAULT NULL

credits INT(1) DEFAULT NULL

The records ...

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Course

id number title credits

1 cs234 Database and Web Development 3

2 cs150 Introduction to Computing II 3

3 cs240 Introduction to Computing III 3

id is the PK

Primary Key = PK

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Each table must have a primary key (PK)

The PK uniquely identifies each record. Each record should be locatable by one and only one PK.

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Course

id

number

title

credits

• Uniquely identifies each row

• Each table should have one

• Use int values when possible

• Could be a composite (two or more fields)

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Foreign Key = FK

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Tables are related via FKFK = PK

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Course

id

number

title

credits

Transcript

student$id

course$id

grade

Three types of relationships

• one-to-many (most popular)

• one-to-one (rare: table too big, security is needed)

• many-to-many (common, must be modeled with two one-to-many)

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One-to-many

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Course

id

number

title

credits

Transcript

student$id

course$id

grade

One record in the primary table is linked to zero or more records in the secondary table.

One-to-one

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Student

id

first

last

StudentPrivate

ssn

student$id

One record in the primary table is linked to zero or one record in the secondary table.

Used primarily for security and when a table is too big and needs to be broken down

Many-to-many

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Course

id

number

title

credits

Transcript

student$id

course$id

grade

Student

id

first

last

One record in the primary may be linked to zero or more records in the secondary table, and one record in the secondary table may be linked to zero or more records in the primary table.

This kind of relationship must be split into two 1-to-many relationships.

Tables must be normalized

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Normalizing is the process by which a table is restructured to eliminate design problems.

Duplication of data is to be dealt with.Ease of searching must be first.Records must be uniquely selectable.

Basically, we want a db that is easy to work with and does not waste space.

Normalization benefits

• No data redundancy

• Data access flexibility

• No inconsistent data

• Removes horizontal/vertical duplication

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Apply three NFs

• 1NF - No horizontal duplication

• atomic fields, no repeating fields

• 2NF - 1NF & No vertical duplication

• fields should depend on entire PK

• 3NF - 2NF & Functional dependence

• fields don't depend on other fields

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1NF - No ⬌ duplication

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Inventory

sid sLoc sZip pNo1 pName1 qty1 pNo2 pName2 qty2

1 Chicago 60632 1 stool 5 2 lamp 15

2 Dallas 75206 1 stool 25 3 desk 10

3 Chicago 60632 2 lamp 10 4 chair 3

No repeating groups within rows No similar fields (ph1, ph2 ...) No multi value fields (first+last)What if more parts need to be stored? Design must changeSpace is waisted if supplier has fewer than two partsQuerying on parts is more difficult

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Inventory

sid sLoc sZip pNo1 pName1 qty1 pNo2 pName2 qty2

1 Chicago 60632 1 stool 5 2 lamp 15

2 Dallas 75206 1 stool 25 3 desk 10

3 Chicago 60632 2 lamp 10 4 chair 3

Inventorysid sLoc sZip pNo pName qty1 Chicago 60632 1 stool 5

1 Chicago 60632 2 lamp 152 Dallas 75206 1 stool 252 Dallas 75206 3 desk 103 Chicago 60632 2 lamp 103 Chicago 60632 4 chair 3

We use a composite PK (sid + pNo)

Now we can have as many parts as needed

2NF - No ⬍ duplication

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Inventorysid sLoc sZip pNo pName qty1 Chicago 60632 1 stool 51 Chicago 60632 2 lamp 152 Dallas 75206 1 stool 252 Dallas 75206 3 desk 103 Chicago 60632 2 lamp 103 Chicago 60632 4 chair 3

2NF: In 1NF and every non-key value is fully dependent on the primary key value.

The part values depend only on the pNo, not the sidThe supplier values depend only on the sid, not the pNoNotice how sid and pNo are repeated vertically

Removing is an issue: If you remove a part, you could be removing the only supplier information on hand.Updating supplier or part data necessitates multi-row updates. Change zip or part name and see what I mean.

A non-key value cannot depend only on some part of the PK

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Supplierid location zipcode1 Chicago 606322 Dallas 752063 Chicago 60632

✅Part

supplier$id id name qty1 1 stool 51 2 lamp 152 1 stool 252 3 desk 103 2 lamp 103 4 chair 3

❌

Inventorysid sLoc sZip pNo pName qty1 Chicago 60632 1 stool 51 Chicago 60632 2 lamp 152 Dallas 75206 1 stool 252 Dallas 75206 3 desk 103 Chicago 60632 2 lamp 103 Chicago 60632 4 chair 3

Vertical repetition can be solved by splitting the table into two. One for supplier and one for part.

Basically each entity should have its own table.

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Partsupplier$id id name qty

1 1 stool 51 2 lamp 152 1 stool 252 3 desk 103 2 lamp 103 4 chair 3

❌

SupplierPartsupplier$id id qty

1 1 51 2 152 1 252 3 103 2 103 4 3

✅Part

id name

1 stool

2 lamp

3 desk

4 chair

✅

The part table is not in 2NF since the part name only depends on the part id and not the sid.

The part table needs to be spit into two.

A supplier supplies many parts and a part (name) can be supplied by many suppliers. A stool for instance is supplied by supplier 1 and 2

This leads to a Part table describing the parts, and an associative table SupplierPart that relates the supplier with the parts it supplies. Notice the qty is an attribute of this table, representing parts on hand.

3NF - PK only describes record

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Partid name1 stool2 lamp3 desk4 chair

✅Supplierid location zipcode1 Chicago 606322 Dallas 752063 Chicago 60632

❌ SupplierPartsupplier$id id qty

1 1 51 2 152 1 252 3 103 2 103 4 3

✅

3NF: In 2NF and every non-key value depends directly on the primary key and not on some other non-key value.

Now, the supplier table is not in 3NF, since zip code depends on location which depends on the PK. Therefore, we must split into two tables.

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Supplierid location zipcode1 Chicago 606322 Dallas 752063 Chicago 60632

❌

Supplierid supplierzip$id1 12 23 1

✅ SupplierZipid location zipcode

1 Chicago 606322 Dallas 75206

✅

3NF: In 2NF and every non-key value depends directly on the primary key and not on some other non-key value.

Recap

• 1NF - don't duplicate across a row

• 2NF - vertical duplication requires splits

• 3NF - functional dependence (PK only), requires splits

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Supplierid supplierzip$id1 12 23 1

SupplierZipid location zipcode1 Chicago 606322 Dallas 75206

SupplierPartsupplier$id part$id qty

1 1 51 2 152 1 252 3 103 2 103 4 3

Partid name1 stool2 lamp3 desk4 chair

Our Normalization method

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ERFeD - say what?

• Identify Entities

• Establish Relations

• Add Fields

• Choose Primary Key

• Select Data Types

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1 Entities

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Our database needs to store supplier locations and part names. The inventory

should store a qty at hand of each partName and its supplier. A location/zip

code can have multiple suppliers.

Supplier PartSupplierPart

SupplierZip

2 Relations

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Notice the crow feet relations that exist

The single bar is on the one-side The crow foot is not the many-side

supplies supplied

includes

Supplier PartSupplierPart

SupplierZip

3 Fields

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supplies supplied

includes

Supplier Part

name

SupplierPart

qty

SupplierZip

location zipcode

4 Primary Key

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supplies supplied

includes

Supplier

id supplierzip$id

Part

id name

SupplierPart

supplier$id part$id qty

SupplierZip

id location zipcode

5 Data types

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Supplierid supplierzip$id

INT NOT NULL AUTO_INCREMENT INT NOT NULL

Partid name

INT NOT NULL AUTO_INCREMENT VARCHAR(25)

SupplierPartsupplier$id part$id qty

INT NOT NULL INT NOT NULL INT NOT NULL

SupplierZipid location zipcode

INT NOT NULL AUTO_INCREMENT VARCHAR(20) NOT NULL VARCHAR(10) NOT NULL

DDL

Data Definition Language

SQL's lingua Franca

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DML

Data ManipulationLanguage

CREATEDB/Table

DDL

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ALTERDB/Table

DROPDB/Table

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Create a database CREATE DATABASE mydb;

Create a database if it does not exist CREATE DATABASE IF NOT EXISTS mydb;

Create a DB with some customization CREATE DATABASE IF NOT EXISTS mydb CHARACTER SET utf8 COLLATE utf8_danish_ci;

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Create a table CREATE TABLE IF NOT EXISTS customer ( id INT UNSIGNED NOT NULL AUTO_INCREMENT, first_name CHAR(30) NOT NULL, last_name CHAR(30) NOT NULL, PRIMARY KEY(id), INDEX (last_name) ) ENGINE=InnoDB;

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CREATE TABLE IF NOT EXISTS order ( customer$id INT UNSIGNED NOT NULL, orderDetails$id INT UNSIGNED NOT NULL date DATE, amount DOUBLE(6,2), PRIMARY KEY(customer$id, orderDetails$id), FOREIGN KEY(customer$id) REFERENCES customer(id), FOREIGN KEY (orderDetails$id) REFERENCES orderDetails(id) ) ENGINE=InnoDB;

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Alter a database's character set and collation ALTER DATABASE mydb CHARACTER SET latin1 COLLATE latin1_swedish_ci;

To see the db's schema SELECT * FROM information_schema.schemata WHERE schema_name = 'mydb'\G mysql> select * from information_schema.schemata -> where schema_name = 'courses'\G*************************** 1. row *************************** CATALOG_NAME: def SCHEMA_NAME: coursesDEFAULT_CHARACTER_SET_NAME: latin1 DEFAULT_COLLATION_NAME: latin1_swedish_ci SQL_PATH: NULL1 row in set (0.00 sec)

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To get a table schema DESCRIBE student;

mysql> describe student;+-------+-------------+------+-----+---------+-------+| Field | Type | Null | Key | Default | Extra |+-------+-------------+------+-----+---------+-------+| id | int(9) | NO | PRI | NULL | || first | varchar(25) | YES | | NULL | || last | varchar(30) | YES | | NULL | |+-------+-------------+------+-----+---------+-------+3 rows in set (0.01 sec)

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ALTER TABLE customer ADD createdOn DATE NOT NULL;

customer

idfirst_namelast_namecreatedOn

customer

idfirst_namelast_name

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ALTER TABLE customer MODIFY last_name CHAR(40) NOT NULL;

customer

idfirst_namelast_name C(40) NNcreatedOn

customer

idfirst_namelast_name C(30) NN

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Drop a database DROP DATABASE mydb;

Drop a database if it exists DROP DATABASE IF EXISTS mydb;

Drop a table DROP TABLE customer;

Drop a table if it exists DROP TABLE IF EXISTS customer;

SELECTrecords

DML

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INSERTrecords

DELETErecords

UPDATErecords

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Select from a single table

SELECT * | field1 [, field2, … fieldn] FROM table [WHERE condition] [ORDER BY field1 [ASC | DESC] [, ...]]

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List all doll names and date purchased, list most recent first.

SELECT Character, DateAcquired FROM Dolls ORDER BY DateAcquired DESC

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List all doll names and date purchased, list most recent first.

SELECT Character, DateAcquired FROM Dolls ORDER BY DateAcquired DESC

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List all the dolls in the $3.00 to $9.00 range, starting with the most expensive; list their name and price. SELECT Character, PurchasePrice FROM Dolls WHERE PurchasePrice >= 3.0 AND PurchasePrice <= 9.0 ORDER BY PurchasePrice DESC

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List all the dolls in the $3.00 to $9.00 range, starting with the most expensive; list their name and price. SELECT Character, PurchasePrice FROM Dolls WHERE PurchasePrice >= 3.0 AND PurchasePrice <= 9.0 ORDER BY PurchasePrice DESC

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List all dolls and makers whose names begin with ‘J’; list their name and manufacturer. SELECT Character, ManufacturerID FROM Dolls WHERE Character LIKE ‘J%’

% - match 0 or more characters_ - match 1 character

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List all dolls and makers whose names begin with ‘J’; list their name and manufacturer. SELECT Character, ManufacturerID FROM Dolls WHERE Character LIKE ‘J*’

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Inner Join - multi-table select

SELECT parent.field,...,child.field,... FROM parent INNER JOIN child ON parent.PK = child.FK [GROUP BY field] [ORDER BY field]

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Where Join - preferred multi-table select

SELECT parent.field,...,child.field,... FROM parent, child WHERE parent.PK = child.FK [GROUP BY field] [ORDER BY field]

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+----+--------+-------------------------------+---------+| id | number | title | credits |+----+--------+-------------------------------+---------+| 1 | CS234 | DATABASE AND WEB DEVELOPMENT | 3 || 2 | CS150 | INTRODUCTION TO COMPUTING II | 3 || 3 | CS240 | INTRODUCTION TO COMPUTING III | 3 |+----+--------+-------------------------------+---------+

+-----------+--------+-------+| id | first | last |+-----------+--------+-------+| 111222111 | first1 | last1 || 111333111 | first2 | last2 || 111444111 | first3 | last3 |+-----------+--------+-------+

+------------+-----------+-------+| student$id | course$id | grade |+------------+-----------+-------+| 111222111 | 1 | A || 111222111 | 2 | B || 111333111 | 3 | C || 111444111 | 1 | B |+------------+-----------+-------+

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list student id, last name, course id and grade SELECT student.id, student.last, transcript.course$id, transcript.grade FROM student, transcript WHERE student.id = transcript.student$id

student

idfirstlast

transcript

course$idstudent$idgrade

course

idnumbertitlecredits

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+-----------+-------+-----------+-------+| id | last | course$id | grade |+-----------+-------+-----------+-------+| 111222111 | last1 | 1 | A || 111222111 | last1 | 2 | B || 111333111 | last2 | 3 | C || 111444111 | last3 | 1 | B |+-----------+-------+-----------+-------+

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list student name, course number and grade SELECT student.first, student.last, course.number, transcript.grade FROM student, course, transcript WHERE student.id = transcript.student$id AND course.id = transcript.course$id

student

idfirstlast

transcript

course$idstudent$idgrade

course

idnumbertitlecredits

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+--------+-------+--------+-------+| first | last | number | grade |+--------+-------+--------+-------+| first1 | last1 | CS234 | A || first1 | last1 | CS150 | B || first2 | last2 | CS240 | C || first3 | last3 | CS234 | B |+--------+-------+--------+-------+

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list student name, course number and grade SELECT s.first, s.last, c.number, t.grade FROM student AS s, course AS c, transcript AS t WHERE s.id = t.student$id AND c.id = t.course$id

student

idfirstlast

transcript

course$idstudent$idgrade

course

idnumbertitlecredits

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+--------+-------+--------+-------+| first | last | number | grade |+--------+-------+--------+-------+| first1 | last1 | CS234 | A || first1 | last1 | CS150 | B || first2 | last2 | CS240 | C || first3 | last3 | CS234 | B |+--------+-------+--------+-------+

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list sid and count of courses taken SELECT student$id AS sid, COUNT(course$id) AS 'Courses Taken' FROM transcript GROUP BY student$id

student

idfirstlast

transcript

course$idstudent$idgrade

course

idnumbertitlecredits

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+-----------+---------------+| sid | Courses Taken |+-----------+---------------+| 111222111 | 2 || 111333111 | 1 || 111444111 | 1 |+-----------+---------------+

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Insert a record into a table

INSERT [INTO] table [(field-list)] VALUES (value-list)[, (value-list)]

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Add the record (‘Hillary Clinton’, ‘MagicPlastic’, 9.95, 11/23,2008 into the Dolls table

INSERT INTO Dolls (Character, ManufacturerID, PurchasePrice, DateAcquired) VALUES ('Hillary Clinton', 'MagicPlastic', 9.95, #11/23/2008#)

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Update some or all the records

UPDATE table SET expression1 [, expression2 …] [WHERE selection-criteria]

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Change Hillary’s name to Chelsea.

UPDATE Dolls SET Character = ‘Chelsea Clinton’ WHERE Character = ‘Hillary Clinton’

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Delete all records from a table DELETE FROM customer;

Delete all records from a table TRUNCATE TABLE customer;

Delete a single record from a table DELETE FROM customer WHERE cid='5';

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Delete Chelsea’s record from Dolls.

DELETE FROM Dolls WHERE Character = ‘Chelsea Clinton’