1. 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
2003
SJSU -- CmpE

2. Structured Query Language (SQL)
Lesson 3 – II:
Structured Query Language (SQL) 2
2003
SJSU – CmpE --- M.E. Fayad

3. 3 Lesson Objectives Explore the history of SQL
Learn how to write queries using SQL 3
2003
SJSU – CmpE --- M.E. Fayad

4. 4 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). 4
2003
SJSU – CmpE --- M.E. Fayad

5. 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 5
2003
SJSU – CmpE --- M.E. Fayad

6. 6 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, , 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. 6
2003
SJSU – CmpE --- M.E. Fayad

7. 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
Backus-Naur Form makes it possible to define SQL (and other programming languages) concisely 7
2003
SJSU – CmpE --- M.E. Fayad

8. 8 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 8
2003
SJSU – CmpE --- M.E. Fayad

9. 9 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" 9
2003
SJSU – CmpE --- M.E. Fayad

10. 10 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 10
2003
SJSU – CmpE --- M.E. Fayad

11. 11 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 11
2003
SJSU – CmpE --- M.E. Fayad

12. 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. 12
2003
SJSU – CmpE --- M.E. Fayad

13. 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)) 13
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SJSU – CmpE --- M.E. Fayad

14. Examples of SQL Commands (3)
DELETE FROM table_name WHERE select_statement
Examples
DELETE FROM employee_names WHERE SSN = " "
DELETE FROM monographs WHERE copyright_date LESS THAN 1910 AND WHERE language = "Dutch" 14
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SJSU – CmpE --- M.E. Fayad

15. Examples of SQL Commands (4)
INSERT INTO table_name [(column_list)] VALUES (value1, value2, ...)
Examples
INSERT INTO employee_names VALUES (" ", "Lee", "Jerry", "07/04/68")
INSERT INTO employee_names (SSN, emp_fname) VALUES (" , "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 " " in the first column, "Socrates" in the third column, and nulls in the second and fourth columns. 15
2003
SJSU – CmpE --- M.E. Fayad

16. 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=" "
SELECT ALL FROM cataloging_staff ORDER BY workstation_num 16
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SJSU – CmpE --- M.E. Fayad

17. 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=" " AND WHERE catlgr_lname = emp_lname AND WHERE catlgr_fname=emp_fname 17
2003
SJSU – CmpE --- M.E. Fayad

18. 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 18
2003
SJSU – CmpE --- M.E. Fayad

19. The World is Full of Files19
SQL Helps Us Handle Them in RDBMSs
2003
SJSU – CmpE --- M.E. Fayad

20. 20 Discussion Questions T/F
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.
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").
ALL, BY, AS, CURRENT are SQL commands.
Aggregate functions are used in conjunction with SQL commands (mainly the SELECT command). 20
2003
SJSU – CmpE --- M.E. Fayad