Download CmpE226-DB-L07n

Database Design
Dr. M.E. Fayad, Professor
Computer Engineering Department, Room #283I
College of Engineering
San José State University
One Washington Square
San José, CA 95192-0180
http://www.engr.sjsu.edu/~fayad
2003
SJSU -- CmpE
L7-S1
SQL
Lesson 07 – II:
Structured Query Language
(SQL)
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M.E. Fayad
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SQL
Lesson Objectives
Objectives

Explore the history of SQL
 Learn how to write queries using SQL
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What Is SQL?

Structured Query Language
– A widely used standard set of commands and
syntax for doing things with RDBMSs
– Used especially for query and retrieval
– Includes commands for defining RDBs, conducting
transactions, storing data, etc.
– Implemented in all major RDBMSs
– SQL does not handle all the practical details
involved in using a RDB. Hence, every RDBMS
has additional features (some of which may form
part of an extension of SQL for that particular
RDBMS).
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L7-S4
SQL
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History of SQL (1)



A prototype DB query and retrieval language
was developed by IBM in the early 1970s as
"Sequel"
Other RDB developers and users recognized
the advantages of having a standard language
for manipulating RDBs
This led to ANSI adoption of SQL as an
enhanced RDB language based on Sequel
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History of SQL (2)

Standardized Versions of SQL
– Work toward an ANSI standard version started in
1983
– Further drafts in 1986 and 1988 led to SQL-1 in 1989
– SQL-2, adopted as an ANSI and ISO standard in
1992, is the version generally used at present
– The latest ANSI-ISO standard, 1998-1999, SQL-3,
has not yet been widely implemented.
• SQL-3 contains new features that help in the
construction of "object-relational" databases, i.e., RDBs
that can handle objects in the technical sense: viz.,
sets of data together with program code that operates
on the data.
2003
SJSU – CmpE ---
M.E. Fayad
L7-S6
SQL
6
Syntax Conventions: Backus-Naur Form


SQL (like other computer languages) is formally defined in
a notation called "Backus-Naur Form"
History of Backus-Naur Form (BNF)
– In 1959 John Backus of IBM devised Backus Normal Form as
a concise notation for describing components of a
programming language (Algol 58, the first high-level
programming language)
– In 1960 Peter Naur, a Danish programmer, refined Backus's
notation
– Result is Backus-Naur Form (the preferred name for for the
notation in current use, though this is still usually called
Backus Normal Form)

Use of BNF
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– Backus-Naur Form makes it possible to define SQL (and other
programming languages) concisely
2003
SJSU – CmpE ---
M.E. Fayad
L7-S7
SQL
Backus-Naur Form (1)

Ingredients of BNF
– When parentheses "()" are provided in the
definition of a command, this tells you that you
must use the parentheses, as shown, when you
write out the command.
– | (vertical bar) means an "exclusive or"; that is,
"either but not both" or "any one but not all"
– "," (comma) means a "nonexclusive or"; that is,
"none, or one, or more than one"
– "..." (ellipses) mean that you may repeat the
previous item as many times as you wish
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M.E. Fayad
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SQL
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Backus-Naur Form (2)

Ingredients of BNF (cont'd)
– "<>" (angle brackets) are used to contain a generic
name for a type of item; they mean that you are to
replace them and their contents by the actual name of
the item named generically between the "<>"
• Example: "SELECT <tablename>" means that if, say,
your RDB contains a table named "students" and you
want to perform a select operation on this table, you
should write
SELECT students
– Note: When confusion is unlikely to occur, angle
brackets are often omitted in definitions of SQL
commands; i.e., you will often see statements like
"SELECT tablename"
2003
SJSU – CmpE ---
M.E. Fayad
L7-S9
SQL
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Backus-Naur Form (3)
 Ingredients
of BNF (cont'd)
– {} (braces) mean you must choose at least
one of the enclosed choices, which may be
separated by "|" or "," (i.e., by an "exclusive
or" or a "non-exclusive or")
– Examples
• {a|b|c} means you must choose exactly one of the
choices
• {a,b,c} means you must choose one or more of
the choices
2003
SJSU – CmpE ---
M.E. Fayad
L7-S10
SQL
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Backus-Naur Form (4)
 Ingredients
of BNF (cont'd)
– [] (brackets) mean that you may choose
one or more of the enclosed choices,
which may be separated by "|" or ","
– Examples
• [a|b|c] means that you may choose at most one
of the choices
• [a,b,c] means that you may choose none, one,
or several of the choices
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SJSU – CmpE ---
M.E. Fayad
L7-S11
SQL
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Examples of SQL Commands (1)

CREATE DATABASE database_name
– Example
• CREATE DATABASE library_catalog
• CREATE DATABASE employees

CREATE INDEX index_name ON table_name
(column_name [, column_name]...)
– Examples
• CREATE INDEX publisher_ndx ON monographs
(pub_name)
• CREATE INDEX name_ndx ON employee_names
(emp_lname, emp_fname)
– Note: This second example shows the creation of a
composite index.
2003
SJSU – CmpE ---
M.E. Fayad
L7-S12
SQL
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Examples of SQL Commands (2)

CREATE TABLE table_name (column_name
datatype [NULL | NOT NULL] [, column_name
datatype [NULL | NOT NULL] ]...)
– Examples
• CREATE TABLE employee_names (SSN CHAR(11)
NOT NULL, emp_lname CHAR(20), emp_fname
CHAR(15), emp_bdate DATE(mm"/"dd"/"yy))
• CREATE TABLE cataloging_staff (catlgr_fname
CHAR(15), catlgr_lname CHAR(20), workstation_num
CHAR(3))
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Examples of SQL Commands (3)
 DELETE
FROM table_name WHERE
select_statement
– Examples
• DELETE FROM employee_names WHERE SSN
= "123-45-6789"
• DELETE FROM monographs WHERE
copyright_date LESS THAN 1910 AND WHERE
language = "Dutch"
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Examples of SQL Commands (4)

INSERT INTO table_name [(column_list)]
VALUES (value1, value2, ...)
– Examples
• INSERT INTO employee_names VALUES ("987-654321", "Lee", "Jerry", "07/04/68")
• INSERT INTO employee_names (SSN, emp_fname)
VALUES ("001-23-4456, "Socrates")
• INSERT INTO cataloging_staff VALUES ("Jerry",
"Lee", "3")
– Note: The first example results in the addition to the
employee_names table of a new row with the entries
specified. The second example will result in the
addition to the employee_names table of a row with
"001-23-4456" in the first column, "Socrates" in the
third column, and nulls in the second and fourth
columns.
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Examples of SQL Commands (5)

SELECT [ALL | DISTINCT] select_col_list FROM
{table_name | view_name} [, {table_name | view_name}]
... [WHERE selection_condition_statement] [GROUP BY
column_name [, column_name]...] [HAVING
search_conditions] [ORDER BY {column_name |
select_list-number} [ASC | DESC] [, {column_name |
select_list_number} [ASC | DESC]...}
– Examples
• SELECT emp_fname, emp_lname FROM employees
WHERE SSN="123-45-6789"
• SELECT ALL FROM cataloging_staff ORDER BY
workstation_num
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SJSU – CmpE ---
M.E. Fayad
L7-S16
SQL
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Examples of SQL Commands (6)

SELECT [ALL | DISTINCT] select_column_list FROM
{table_name | view_name} [, {table_name | view_name}]
... [WHERE selection_condition_statement] [GROUP BY
column_name [, column_name]...] [HAVING
search_conditions] [ORDER BY {column_name |
select_list-number} [ASC | DESC] [, {column_name |
select_list_number} [ASC | DESC]...}
– Example
• SELECT SSN, emp_fname, emp_lname,
workstation_num FROM employees, cataloging_staff
WHERE SSN="987-65-4321" AND WHERE
catlgr_lname = emp_lname AND WHERE
catlgr_fname=emp_fname
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SJSU – CmpE ---
M.E. Fayad
L7-S17
SQL
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Examples of SQL Commands (7)

SELECT [ALL | DISTINCT] select_column_list FROM
{table_name | view_name} [, {table_name |
view_name}] ... [WHERE
selection_condition_statement] [GROUP BY
column_name [, column_name]...] [HAVING
search_conditions] [ORDER BY {column_name |
select_list-number} [ASC | DESC] [, {column_name |
select_list_number} [ASC | DESC]...}
– Example
• SELECT mono_title FROM monographs WHERE
au_lname="Asimov" AND au_fname="Isaac"
GROUP BY fict_non_fict_marker ORDER BY
mono_title asc
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SQL
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The World is Full of Files
SQL Helps Us Handle Them in RDBMSs
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M.E. Fayad
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SQL
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Discussion Questions
T/F
1.
SQL has become more than a mere query language; it has
evolved into a language that is also used for defining databases
and their contents.
2.
The SQL contains commands, arithmetic expressions, keywords,
logical connectives, and predicates (i.e., conditions that are
evaluated to yield values of "true," "false", or "unknown").
3.
ALL, BY, AS, CURRENT are SQL commands.
4.
Aggregate functions are used in conjunction with SQL commands
(mainly the SELECT command).
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L7-S20
SQL