SQL and Client Applications

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SQL and Client Applications

• University of California, Berkeley
• School of Information
• IS 257 Database Management

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Lecture Outline

• Review
• Relational Operations
• Relational Algebra
• Relational Calculus
• Introduction to SQL
• Introduction to SQL (continued)
• Application Development in Access

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Lecture Outline

• Review
• Relational Operations
• Relational Algebra
• Relational Calculus
• Introduction to SQL
• Introduction to SQL (continued)
• Application Development in Access

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Relational Algebra Operations

• Select
• Project
• Product
• Union
• Intersect
• Difference
• Join
• Divide

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Select

• Extracts specified tuples (rows) from a specified
  relation (table).

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Project

• Extracts specified attributes(columns) from a
  specified relation.

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Join

• Builds a relation from two specified relations
  consisting of all possible concatenated pairs,
  one from each of the two relations, such that in
  each pair the two tuples satisfy some condition.
  (E.g., equal values in a given col.)

(Natural or Inner) Join
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Outer Join

• Outer Joins are similar to PRODUCT -- but will
  leave NULLs for any row in the first table with
  no corresponding rows in the second.

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Join Items
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Relational Algebra

• What is the name of the customer who ordered
  Large Red Widgets?
• Select large Red Widgets from Part as temp1
• Join temp1 with Line-item on Part as temp2
• Join temp2 with Invoice on Invoice as temp3
• Join temp3 with customer on cust as temp4
• Project Name from temp4

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Relational Calculus

• Relational Algebra provides a set of explicit
  operations (select, project, join, etc) that can
  be used to build some desired relation from the
  database.
• Relational Calculus provides a notation for
  formulating the definition of that desired
  relation in terms of the relations in the
  database without explicitly stating the
  operations to be performed
• SQL is based on the relational calculus.

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SQL - History

• Structured Query Language
• SEQUEL from IBM San Jose
• ANSI 1992 Standard is the version used by most
  DBMS today (SQL92)
• Basic language is standardized across relational
  DBMSs. Each system may have proprietary
  extensions to standard.

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Lecture Outline

• Review
• Relational Operations
• Relational Algebra
• Relational Calculus
• Introduction to SQL
• Introduction to SQL (continued)
• Application Development in Access

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SQL Uses

• Database Definition and Querying
• Can be used as an interactive query language
• Can be imbedded in programs
• Relational Calculus combines Select, Project and
  Join operations in a single command SELECT

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SELECT

• Syntax
• SELECT DISTINCT attr1, attr2,, attr3 FROM
  rel1 r1, rel2 r2, rel3 r3 WHERE condition1 AND
  OR condition2 ORDER BY attr1 DESC, attr3
  DESC

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SELECT

• Syntax
• SELECT a.author, b.title FROM authors a, bibfile
  b, au_bib c WHERE a.AU_ID c.AU_ID and c.accno
  b.accno ORDER BY a.author
• Examples in Access...

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SELECT Conditions

• equal to a particular value
• gt greater than or equal to a particular value
• gt greater than a particular value
• lt less than or equal to a particular value
• ltgt not equal to a particular value
• LIKE term (may be other wild cards in other
  systems)
• IN (opt1, opt2,,optn)
• BETWEEN val1 AND val2
• IS NULL

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Relational Algebra Selection using SELECT

• Syntax
• SELECT FROM rel1 WHERE condition1 AND OR
  condition2

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Relational Algebra Projection using SELECT

• Syntax
• SELECT DISTINCT attr1, attr2,, attr3 FROM
  rel1 r1, rel2 r2, rel3 r3

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Relational Algebra Join using SELECT

• Syntax
• SELECT FROM rel1 r1, rel2 r2 WHERE r1.linkattr
  r2.linkattr

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Sorting

• SELECT BIOLIFE.Common Name, BIOLIFE.Length
  (cm)
• FROM BIOLIFE
• ORDER BY BIOLIFE.Length (cm) DESC

Note the square brackets are not part of the
standard, But are used in Access for names with
embedded blanks
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Subqueries

• SELECT SITES.Site Name, SITES.Destination no
• FROM SITES
• WHERE sites.Destination no IN (SELECT
  Destination no from DEST where avg temp (f)
  gt 78)
• Can be used as a form of JOIN.

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Aggregate Functions

• Count
• Avg
• SUM
• MAX
• MIN
• Others may be available in different systems

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Using Aggregate functions

• SELECT attr1, Sum(attr2) AS name
  FROM tab1, tab2 ...
• GROUP BY attr1, attr3 HAVING condition

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Using an Aggregate Function

• SELECT DIVECUST.Name, Sum(Priceqty) AS Total
• FROM (DIVECUST INNER JOIN DIVEORDS ON
  DIVECUST.Customer No DIVEORDS.Customer No)
  INNER JOIN DIVEITEM ON DIVEORDS.Order No
  DIVEITEM.Order No
• GROUP BY DIVECUST.Name
• HAVING (((DIVECUST.Name) Like "Jazdzewski"))

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GROUP BY

• SELECT DEST.Destination Name, Count() AS Expr1
• FROM DEST INNER JOIN DIVEORDS ON
  DEST.Destination Name DIVEORDS.Destination
• GROUP BY DEST.Destination Name
• HAVING ((Count())gt1)
• Provides a list of Destinations with the number
  of orders going to that destination

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Lecture Outline

• Review
• Relational Operations
• Relational Algebra
• Relational Calculus
• Introduction to SQL
• Introduction to SQL (continued)
• Application Development in Access

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ORACLE Examples

• Logging in
• Starting SQLPLUS
• Running SQL queries against my copies of the
  Diveshop database
• settings for readability
• creating SQLPLUS scripts

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CREATE Table

• CREATE TABLE table-name (attr1 attr-type
  PRIMARYKEY, attr2 attr-type,,attrN attr-type)
• Adds a new table with the specified attributes
  (and types) to the database.

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Access Data Types

• Numeric (1, 2, 4, 8 bytes, fixed or float)
• Text (255 max)
• Memo (64000 max)
• Date/Time (8 bytes)
• Currency (8 bytes, 15 digits 4 digits decimal)
• Autonumber (4 bytes)
• Yes/No (1 bit)
• OLE (limited only by disk space)
• Hyperlinks (up to 64000 chars)

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Access Numeric types

• Byte
• Stores numbers from 0 to 255 (no fractions). 1
  byte
• Integer
• Stores numbers from 32,768 to 32,767 (no
  fractions) 2 bytes
• Long Integer (Default)
• Stores numbers from 2,147,483,648 to
  2,147,483,647 (no fractions). 4 bytes
• Single
• Stores numbers from -3.402823E38 to 1.401298E45
  for negative values and from 1.401298E45 to
  3.402823E38 for positive values. 4 bytes
• Double
• Stores numbers from 1.79769313486231E308 to
  4.94065645841247E324 for negative values and
  from 1.79769313486231E308 to 4.94065645841247E324
  for positive values. 15 8 bytes
• Replication ID
• Globally unique identifier (GUID) N/A 16 bytes

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Oracle Data Types

• CHAR (size) -- max 2000
• VARCHAR2(size) -- up to 4000
• DATE
• DECIMAL, FLOAT, INTEGER, INTEGER(s), SMALLINT,
  NUMBER, NUMBER(size,d)
• All numbers internally in same format
• LONG, LONG RAW, LONG VARCHAR
• up to 2 Gb -- only one per table
• BLOB, CLOB, NCLOB -- up to 4 Gb
• BFILE -- file pointer to binary OS file

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Creating a new table from existing tables

• Syntax
• SELECT DISTINCT attr1, attr2,, attr3 INTO
  newtablename FROM rel1 r1, rel2 r2, rel3 r3
  WHERE condition1 AND OR condition2 ORDER BY
  attr1 DESC, attr3 DESC

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ALTER Table

• ALTER TABLE table-name ADD COLUMN attr1
  attr-type
• DROP COLUMN attr1
• Adds a new column to an existing database table.

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INSERT

• INSERT INTO table-name (attr1, attr4, attr5,,
  attrK) VALUES (val1, val4, val5,, valK)
• Adds a new row(s) to a table.
• INSERT INTO table-name (attr1, attr4, attr5,,
  attrK) VALUES SELECT ...

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DELETE

• DELETE FROM table-name WHERE ltwhere clausegt
• Removes rows from a table.

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UPDATE

• UPDATE tablename SET attr1newval, attr2
  newval2 WHERE ltwhere clausegt
• changes values in existing rows in a table (those
  that match the WHERE clause).

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DROP Table

• DROP TABLE tablename
• Removes a table from the database.

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CREATE INDEX

• CREATE UNIQUE INDEX indexname ON tablename
  (attr1 ASCDESC, attr2 ASCDESC, ...) WITH
  PRIMARY DISALLOW NULL IGNORE NULL

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Lecture Outline

• Review
• Relational Operations
• Relational Algebra
• Relational Calculus
• Introduction to SQL
• Introduction to SQL (continued)
• Application Development in Access

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Database Applications

• Generally, end-users of database data probably do
  not want to learn SQL in order to access the
  information in the database
• Instead, they would prefer to use a familiar PC
  or Web interface that uses the graphical
  conventions and behaviors that they are familiar
  with
• Today we will look at PC style client
  applications using systems like Access
• Next time we will look at Web-based systems

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Query-by-Example

• QBE was developed in the 1970s as a simpler to
  use interface for IBM mainframe databases
• In QBE the user puts parts of what they want to
  get from the database into a form similar to what
  the output will look like
• The Query Design View in Access is an example of
  QBE

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Access Usability Hierarchy
API
VBA
MACROS
Functions/Expressions
Objects Tables, queries Forms, Reports
From McFadden Chap. 10
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Examples

• Access OBJECT level
• QBE querying
• Building Application interfaces
• User wants point and click and forms to fill
  in, not a Query editing screen or wizard
• How to build them
• Drag and drop as in Access
• Programming Languages
• 4th Generation languages (more on these later)

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The MS JET Database Engine
Adapted from Roman, Access Database Design and
Programming
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Using Access for Applications

• Forms
• Reports
• Macros
• VBA programming
• Application framework
• HTML Pages