Transcript Query-By-Example

Query-By-Example
Ping Zhou
2008.3
Introduction to QBE
Query-By-Example
 A high-level database management
language
 Alternation to SQL for querying relational
database
 Can be translated to SQL
 Developed at IBM (M. Zloof)

◦ Many Databases have QBE-like extension
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Why QBE?
Convenient and unified way to query,
update, define and control database
 Requires little knowledge to the user,
minimizes the concepts user needs to
learn
 Simple yet wide coverage of transactions
 Graphical and tabular interface

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Basic Concepts

Instead of writing text SQL commands…
◦ Programming is done within 2-D “skeleton
tables”
◦ Constant vs Variable
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Basic Queries (1)

Print the names and ages of all sailors…
Variables that appear only once
can be omitted
Shorthand to print all fields
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Basic Queries (2)

Selections – Place constant in some field
Print all sailors with rating=10
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Ordering and Grouping

Order the answer using AO (ascending
order) or DO (descending order)
Duplicate tuples can be
eliminated by using UNO.
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Queries Over Multiple Relations

Select tuples from two relations by
placing same variable at join column
Find sailors who reserved a boat for 8/24/96, and
who are older than 25.
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Select Using Condition Box

Condition box
◦ Express a condition involving two or more columns.
E.g.: _R/_A > 0.2
◦ Express a condition involving aggregate operation on
a group
◦ Express a condition involving AND and OR operators
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Unnamed Columns

Create unnamed column for display

Display fields from more than one tables
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Updating Tables using QBE (1)
Insertion, Deletion and Updating are done
in the same way in QBE
 Insertion

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Updating Tables using QBE (2)

Deleting

Updating
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Changes Brought by QBE

User Interface
◦ Text command -> Graphical, Tabular
◦ User draw the table he wants directly

Easier to learn
◦ Higher scores than SQL users in paper and
pencil testing
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QBE / OBE

OBE: Office Procedure by Example
◦ Incorporate QBE into office automation
◦ Research project developed by IBM
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Spatial QBE

Adding spatial extension to QBE
Retrieve all
ATMs along
Route 64
Retrieve all
banks within 100
meters from
Washington
Hotel.
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Multimedia Queries with QBE

Similarity function
Find all oil paintings from a Dutch painter which
are similar to the given picture.
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References
Query-By-Example: a data base language, M. Zloof, 1977
 Query-By-Example (QBE),
http://pages.cs.wisc.edu/~dbbook/openAccess/thirdEditi
on/qbe.pdf
 A Human Factors Experimental Comparison of SQL
and QBE, Minnie Yi-Miin Yen and Richard W. Scamell,
1993
 Spatial QBE Interface for Web GIS, Shapiee Abd Rahman,
Subhash Bhalla, 2005
 WS-QBE: A QBE-like Query Language for Complex
Multimedia Queries, Ingo Schmitt, Nadine Schulz,
Thomas Herstel, 2005

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THANK YOU!
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