DBMS 3. course

Reminder Data independence: logical and physical Concurrent processing – Transaction – Deadlock – Rollback – Logging ER Diagrams

Decision in design – Entity or attribute? – Entity or relationship? – Binary or ternary relationship?

Today Relational algebra Relational calculus SQL DDL

Relational Query Languages

Formal relational query languages 2 formalisms – Relational algebra – Relational calculus They substantiate the implementation level and the concrete query language (e.g. SQL)

Example Sailors Boats Reserves R S B bidbnamecolor 101Santa MariaBlack 102PintaYellow 103NinaWhite sidsnameratingage 22dustin lubber rusty sidbidday /09/ /09/13

Relational algebra

Goal Describes the way of procedure of the relations Execution plan

Basic operations

Consequent operations a1a1 b1b1 a1a1 b2b2 a1a1 b3b3 a1a1 b4b4 a2a2 b1b1 a2a2 b3b3 a3a3 b2b2 a3a3 b3b3 a3a3 b4b4 a4a4 b1b1 a4a4 b2b2 a4a4 b3b3 b1b1 b2b2 b3b3 a1a1 a4a4

Interpretation of quotient

How to get the quotient

Example ab ed

Join

General join

Natural join visually

Practice

Practical example Cars (C): plate no, manufacturer, type, color People (P): ID, name, job, address Owns (O): car, people_id Task: query the job of the owners of the blue Audis

Steps

SQL – 1. blue Audis, projection SELECT * FROM C WHERE color=’blue’ AND type=’Audi’ SELECT plate_no FROM C WHERE color=’blue’ AND type=’Audi’

SQL – 2. join with O, projection SELECT * FROM (SELECT plate_no FROM C WHERE color=’blue’ AND type=’Audi’) inner_table1 INNER JOIN O ON (O.car=inner_table1.plate_no) SELECT people_ID as ID FROM (SELECT plate_no FROM C WHERE color=’blue’ AND type=’Audi’) inner_table1 INNER JOIN O ON (O.car=inner_table1.plate_no)

SQL – 3. join with table P SELECT * FROM (SELECT people_ID as ID FROM (SELECT plate_no FROM C WHERE color=’blue’ AND type=’Audi’) INNER JOIN O ON (O.car=C.plate_no) inner_table2 INNER JOIN P USING (ID)

SQL – 4. projection SELECT job FROM (SELECT people_ID as ID FROM (SELECT plate_no FROM C WHERE color=’blue’ AND type=’Audi’) INNER JOIN O ON (O.car=C.plate_no)) INNER JOIN P USING (ID)

Relational calculus

Goal

Atomic formulas

Formulas

Example

Example no. 2

Finally Relational algebra and relational calculus can express the same Declarative part is user-friendly The algebra (way of calculation) is the task of the DB

SQL

History of SQL and dialects Main advantage: simple and efficient query DBMS does the evaluation – Semantics – DBMS can (re)order the operations to optimize – Solution set has to be the same

Development SQL-86 SQL-89 (smaller change) SQL-92 (bigger change) SQL:1999 (significantly extended) SQL:2003 (slighly extended) SQL:2008 (splitted into parts, extended) SQL:2011 (newest, most of the DBMSs cannot use)

20 April 2009

27 January 2010

Sun?

Queries Structured Query Language (SQL) – 4 parts Data Definition Language (DDL): CREATE and ALTER tables, views, and indexes Data Manipulation Language (DML): INSERT, UPDATE, and DELETE records Data Control Language (DCL): GRANT and REVOKE permissions, COMMIT and ROLLBACK transactions Query Language: SELECT

DDL – Data Definition Language Tables – CREATE TABLE – ALTER TABLE – DROP TABLE Views – CREATE VIEW – DROP VIEW Indexes – CREATE [UNIQUE] INDEX – DROP INDEX

Syntaxis CREATE TABLE name (attribute description, … key foreign key(s), constraints (table, column), indexes)

CREATE TABLE name (attribute description, … PRIMARY KEY, UNIQUE – unique/secondary key (column) FOREIGN KEY – relationship with other table CHECK – constraints for columns (attributes), CREATE INDEX …)

Primary key Has to be – Unique – Cannot be NULL – In many cases an unsigned integer AUTO_INCREMENT – Increased automatically when inserted

Creating relations (tables) The domain of the attributes is given DBMS validates the domain constraints on every insertion CREATE TABLE Students (sid: CHAR(20), name: CHAR(20), login: CHAR(10), age: INTEGER, gpa: REAL ) CREATE TABLE Enrolled (sid: CHAR(20), cid: CHAR(20), grade: CHAR (2))

Data types in Oracle Everything is stored in tables char(N) – varchar(N) – varchar2(N) blob (vs. clob, ~2-4GB) numeric(N[, M]) / number(N[, M]) / int, float date / timestamp

Data types in MySQL char(N) – varchar(N) blob vs. text: tiny~, ~, medium~, long~, max. 4GB) [signed/ unsigned] tinyint (sbyte), smallint (integer), int, bigint (long), float, double date / time / datetime / timestamp /year – DATE: YYYY-MM-DD – DATETIME: YYYY-MM-DD HH:MM:SS – TIMESTAMP: YYYY-MM-DD HH:MM:SS – TIME: HH:MM:SS – YEAR: YYYY

DROP and ALTER tables DROP TABLE Students ALTER TABLE Students ADD firstYear: integer

Example CREATE TABLE animals ( name VARCHAR2(25), species VARCHAR2(20), gender CHAR(1), born DATE, died DATE);

Giving primary key ALTER TABLE animals ADD ID INTEGER Unsigned PRIMARY KEY AUTO_INCREMENT FIRST;

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