1. CPSC-310 Database Systems
Professor Jianer Chen
Room 315C HRBB
Lecture #21

2. Outline of Course Representing things by tables E-R model (Ch. 4)
Good table structures
Functional Dependencies (Ch.3)
Basic operations on relations
Relational Algebra (Chs. 2+5)
Storage management
(Chs )
SQL languages in DDL/DML
(Ch. 6)
How does SQL get executed
(Chs )
More on SQL
(Chs. 7-9)
Transition processing
(Chs )

3. How does SQL get executed?

4. How does SQL get executed?
DBMS translates a SQL program P into executable code, by

5. How does SQL get executed?
DBMS translates a SQL program P into executable code, by
Preparing a collection C of algorithms for operations in relational algebra;

6. How does SQL get executed?
DBMS translates a SQL program P into executable code, by
Preparing a collection C of algorithms for operations in relational algebra;
For the given SQL program P:
1. understanding the program P;

7. How does SQL get executed?
DBMS translates a SQL program P into executable code, by
Preparing a collection C of algorithms for operations in relational algebra;
For the given SQL program P:
1. understanding the program P;
2. translating P into an expression tree E;

8. How does SQL get executed?
DBMS translates a SQL program P into executable code, by
Preparing a collection C of algorithms for operations in relational algebra;
For the given SQL program P:
1. understanding the program P;
2. translating P into an expression tree E;
3. converting E into an algorithm using algorithms in C.

9. How does SQL get executed?
DBMS translates a SQL program P into executable code, by
Preparing a collection C of algorithms for operations in relational algebra;
For the given SQL program P:
1. understanding the program P;
2. translating P into an expression tree E;
3. converting E into an algorithm using algorithms in C.
Taking care of issues in optimization, consistency, and security.

10. How does SQL get executed?
SELECT a1, b1
FROM A, B
WHERE a2=b2
An SQL program P
Prepare a collection C of efficient algorithms for operations in relational algebra;
Translated by
DBMS
take care of issues in optimization and security. …
Read(A), Read(B);
C = A + B; Write(C)
Machine executable code

11. How does SQL get executed?
SELECT a1, b1
FROM A, B
WHERE a2=b2
An SQL program P
Prepare a collection C of efficient algorithms for operations in relational algebra;
Understand P
A parse tree T
Translate P into an expression tree E
expression tree E
Use the algorithms in C to convert E into executable code
take care of issues in optimization and security. …
Read(A), Read(B);
C = A + B; Write(C)
Machine executable code

12. How does SQL get executed?
SELECT a1, b1
FROM A, B
WHERE a2=b2
An SQL program P
Prepare a collection C of efficient algorithms for operations in relational algebra;
Understand P
A parse tree T
Translate P into an expression tree E
expression tree E
Use the algorithms in C to convert E into executable code
take care of issues in optimization and security. …
Read(A), Read(B);
C = A + B; Write(C)
Machine executable code

13. SELECT beer FROM Likes, Frequents WHERE Frequents. drinker = Likes
SELECT beer FROM Likes, Frequents WHERE Frequents.drinker = Likes.drinker;
SQL program P

14. SELECT beer FROM Likes, Frequents WHERE Frequents. drinker = Likes
SELECT beer FROM Likes, Frequents WHERE Frequents.drinker = Likes.drinker;
SQL program P
select-statement
SELECT
FROM
WHERE
search-condition
boolean-term
boolean-factor
boolean-primary
comparison-predicte
expression
comp-op =
term
column-name
Frequents.drinker
Likes.drinker
table-list
table-name ,
Linkes
Frequents
select-list
select-sublist
beer
Parse tree T

15. SELECT beer FROM Likes, Frequents WHERE Frequents. drinker = Likes
SELECT beer FROM Likes, Frequents WHERE Frequents.drinker = Likes.drinker;
SQL program P
select-statement
SELECT
FROM
WHERE
search-condition
boolean-term
boolean-factor
boolean-primary
comparison-predicte
expression
comp-op =
term
column-name
Frequents.drinker
Likes.drinker
table-list
table-name ,
Linkes
Frequents
select-list
select-sublist
beer
Parse tree T
select-statement ::= SELECT [DISTINCT] select-list
FROM table-list
[WHERE search-condition]
[ORDER BY column-name]
select-list ::= * | select-sublist
select-sublist ::= column-name | column-name, select-sublist
table-list ::= table-name | table-name, table-list
search-condition ::= boolean-term | ……
boolean-term ::= boolean-factor | ……
boolean-factor ::= [NOT] boolean-primary
boolean-primary ::= comparison-predicate | ……
comparison-predicate ::= expression comp-op expression
expression ::= term | ……| ……
term ::= column-name | … | … | …

16. How does SQL get executed?
SELECT a1, b1
FROM A, B
WHERE a2=b2
An SQL program P
Prepare a collection C of efficient algorithms for operations in relational algebra;
Understand P
A parse tree T
Translate P into an expression tree E
expression tree E
Use the algorithms in C to convert E into executable code
take care of issues in optimization and security. …
Read(A), Read(B);
C = A + B; Write(C)
Machine executable code

17. How does SQL get executed?
SELECT a1, b1
FROM A, B
WHERE a2=b2
An SQL program P
Prepare a collection C of efficient algorithms for operations in relational algebra;
select-statement
SELECT
FROM
WHERE
select-list a1 , b1
table-list A B
search-condition a2 = b2
Understand P
A parse tree T
Translate P into an expression tree E
expression tree E
Use the algorithms in C to convert E into executable code
take care of issues in optimization and security. …
Read(A), Read(B);
C = A + B; Write(C)
Machine executable code

18. How does SQL get executed?
SELECT a1, b1
FROM A, B
WHERE a2=b2
An SQL program P
Prepare a collection C of efficient algorithms for operations in relational algebra;
select-statement
SELECT
FROM
WHERE
select-list a1 , b1
table-list A B
search-condition a2 = b2
Understand P
A parse tree T
Translate P into an expression tree E
expression tree E
Use the algorithms in C to convert E into executable code
take care of issues in optimization and security. …
Read(A), Read(B);
C = A + B; Write(C)
Machine executable code

19. How does SQL get executed?
SELECT a1, b1
FROM A, B
WHERE a2=b2
An SQL program P
Prepare a collection C of efficient algorithms for operations in relational algebra;
select-statement
SELECT
FROM
WHERE
select-list a1 , b1
table-list A B
search-condition a2 = b2
Understand P
A parse tree T
Translate P into an expression tree E A B × σ π
a1, b1
a2=b2
expression tree E
Use the algorithms in C to convert E into executable code
take care of issues in optimization and security. …
Read(A), Read(B);
C = A + B; Write(C)
Machine executable code

20. How does SQL get executed?
SELECT a1, b1
FROM A, B
WHERE a2=b2
An SQL program P
Prepare a collection C of efficient algorithms for operations in relational algebra;
select-statement
SELECT
FROM
WHERE
select-list a1 , b1
table-list A B
search-condition a2 = b2
Understand P
A parse tree T
Translate P into an expression tree E A B × σ π
a1, b1
a2=b2 A B ⨝ π
a1, b1
expression tree E
Use the algorithms in C to convert E into executable code
take care of issues in optimization and security. …
Read(A), Read(B);
C = A + B; Write(C)
Machine executable code

21. How does SQL get executed?
SELECT a1, b1
FROM A, B
WHERE a2=b2
An SQL program P
Prepare a collection C of efficient algorithms for operations in relational algebra;
select-statement
SELECT
FROM
WHERE
select-list a1 , b1
table-list A B
search-condition a2 = b2
Understand P
A parse tree T
Translate P into an
expression tree E A B × σ π
a1, b1
a2=b2 A B ⨝ π
a1, b1
Optimization
expression tree E
Use the algorithms in C to convert E into executable code
take care of issues in optimization and security. …
Read(A), Read(B);
C = A + B; Write(C)
Machine executable code

22. How does SQL get executed?
SELECT a1, b1
FROM A, B
WHERE a2=b2
An SQL program P
Prepare a collection C of efficient algorithms for operations in relational algebra;
select-statement
SELECT
FROM
WHERE
select-list a1 , b1
table-list A B
search-condition a2 = b2
Understand P
A parse tree T
Translate P into an
expression tree E A B × σ π
a1, b1
a2=b2 A B ⨝ π
a1, b1
Optimization
expression tree E
Use the algorithms in C to convert E into executable code
take care of issues in optimization and security. …
Read(A), Read(B);
C = A + B; Write(C)
Machine executable code

23. How does SQL get executed?
SELECT a1, b1
FROM A, B
WHERE a2=b2
An SQL program P
Prepare a collection C of efficient algorithms for operations in relational algebra;
select-statement
SELECT
FROM
WHERE
select-list a1 , b1
table-list A B
search-condition a2 = b2
Understand P
A parse tree T
Translate P into an
expression tree E A B × σ π
a1, b1
a2=b2 A B ⨝ π
a1, b1
Optimization
expression tree E
Use the algorithms in C to convert E into executable code
Read(A)
Read(B)
Join
Proj(a1,b1)
take care of issues in optimization and security. …
Read(A), Read(B);
C = A + B; Write(C)
Machine executable code

24. How does SQL get executed?
SELECT a1, b1
FROM A, B
WHERE a2=b2
An SQL program P
Prepare a collection C of efficient algorithms for operations in relational algebra;
select-statement
SELECT
FROM
WHERE
select-list a1 , b1
table-list A B
search-condition a2 = b2
Understand P
A parse tree T
Translate P into an
expression tree E A B × σ π
a1, b1
a2=b2 A B ⨝ π
a1, b1
Optimization
Proj(T, a1,b1) …
Loop
get the next tuple t in T;
output t’s attributes a1 and b1 ….
expression tree E
Use the algorithms in C to convert E into executable code
Read(A)
Read(B)
Join
Proj(a1,b1)
Join(A, B) …
Loop
get the next tuple pair tA, tB;
If tA and tB are joinable
Then output the joined tuple; ….
take care of issues in optimization and security. …
Read(A), Read(B);
C = A + B; Write(C)
Machine executable code

25. How does SQL get executed?
SELECT a1, b1
FROM A, B
WHERE a2=b2
An SQL program P
Prepare a collection C of efficient algorithms for operations in relational algebra;
select-statement
SELECT
FROM
WHERE
select-list a1 , b1
table-list A B
search-condition a2 = b2
Understand P
A parse tree T
Translate P into an
expression tree E A B × σ π
a1, b1
a2=b2 A B ⨝ π
a1, b1
Optimization
Proj(T, a1,b1) …
Loop
get the next tuple t in T;
output t’s attributes a1 and b1 ….
expression tree E
Read(A)
Read(B)
Join
Proj(a1,b1)
Use algorithms in
C to convert E
Join(A, B) …
Loop
get the next tuple pair tA, tB;
If tA and tB are joinable
Then output the joined tuple; ….
take care of issues in optimization and security.
Optimization …
Read(A), Read(B);
C = A + B; Write(C)
Machine executable code

26. How does SQL get executed?
SELECT a1, b1
FROM A, B
WHERE a2=b2
An SQL program P
Prepare a collection C of efficient algorithms for operations in relational algebra;
select-statement
SELECT
FROM
WHERE
select-list a1 , b1
table-list A B
search-condition a2 = b2
Understand P
A parse tree T
Translate P into an
expression tree E A B × σ π
a1, b1
a2=b2 A B ⨝ π
a1, b1
Optimization
Proj(T, a1,b1) …
Loop
get the next tuple t in T;
output t’s attributes a1 and b1 ….
expression tree E
Read(A)
Read(B)
Join
Proj(a1,b1)
Use algorithms in
C to convert E
Join(A, B) …
Loop
get the next tuple pair tA, tB;
If tA and tB are joinable
Then output the joined tuple; ….
take care of issues in optimization and security.
Optimization …
Read(A), Read(B);
C = A + B; Write(C)
Machine executable code

27. Outline of Course Representing things by tables E-R model (Ch. 4)
Good table structures
Functional Dependencies (Ch.3)
Basic operations on relations
Relational Algebra (Chs. 2+5)
Storage management
(Chs )
SQL languages in DDL/DML
(Ch. 6)
How does SQL get executed
(Chs )
More on SQL
(Chs. 7-9)
Transition processing
(Chs )

28. Outline of Course A Related Question: How can SQL be
Executed with conventional
Programming languages?
Representing things by tables
E-R model (Ch. 4)
Good table structures
Functional Dependencies (Ch.3)
Basic operations on relations
Relational Algebra (Chs. 2+5)
Storage management
(Chs )
SQL languages in DDL/DML
(Ch. 6)
How does SQL get executed
(Chs )
More on SQL
(Chs. 7-9)
Transition processing
(Chs )

29. SQL in Real Programs
We have seen only how SQL is used at the generic query interface --- an environment where we sit at a terminal and enters queries to a database.

30. SQL in Real Programs
We have seen only how SQL is used at the generic query interface --- an environment where we sit at a terminal and enters queries to a database.
This is very rare in practice.

31. Goods and Bads of SQL

32. Goods and Bads of SQL
Shortcomings of SQL:

33. Goods and Bads of SQL Shortcomings of SQL:
* Relational data model doesn't match well with data model of conventional programming languages (e.g., data structure mismatch)

34. Goods and Bads of SQL Shortcomings of SQL:
* Relational data model doesn't match well with data model of conventional programming languages (e.g., data structure mismatch)
* No pointers, loops or branches in SQL

35. Goods and Bads of SQL Shortcomings of SQL:
* Relational data model doesn't match well with data model of conventional programming languages (e.g., data structure mismatch)
* No pointers, loops or branches in SQL
* No convenient input and output (e.g. formatting)

36. Goods and Bads of SQL Shortcomings of SQL:
* Relational data model doesn't match well with data model of conventional programming languages (e.g., data structure mismatch)
* No pointers, loops or branches in SQL
* No convenient input and output (e.g. formatting)
Strength of SQL:
* provides strong, easy-to-use/understand, very efficient processing for large volume of data.

37. Goods and Bads of SQL Shortcomings of SQL:
* Relational data model doesn't match well with data model of conventional programming languages (e.g., data structure mismatch)
* No pointers, loops or branches in SQL
* No convenient input and output (e.g. formatting)
Strength of SQL:
* provides strong, easy-to-use/understand, very efficient processing for large volume of data.
Combining conventional programming languages
with SQL allows to do anything computable, yet still
get the very-high-level SQL interface to database

38. Combining SQL and Conventional Programming Languages
Three ways to combine:

39. Combining SQL and Conventional Programming Languages
Three ways to combine:
Persistent Stored Modules (PSM): Code stored in the DB schema and executed on command from a user

40. Combining SQL and Conventional Programming Languages
Three ways to combine:
Persistent Stored Modules (PSM): Code stored in the DB schema and executed on command from a user
Embed SQL statements in programs written in some conventional language

41. Combining SQL and Conventional Programming Languages
Three ways to combine:
Persistent Stored Modules (PSM): Code stored in the DB schema and executed on command from a user
Embed SQL statements in programs written in some conventional language
Call-level interfaces (CLI)
* SQL/CLI (SQL standard, for use with C
* JDBC (for use with Java)

42. Combining SQL and Conventional Programming Languages
Three ways to combine:
Persistent Stored Modules (PSM): Code stored in the DB schema and executed on command from a user
Embed SQL statements in programs written in some conventional language
Call-level interfaces (CLI)
* SQL/CLI (SQL standard, for use with C
* JDBC (for use with Java)

43. Persistent Stored Modules (PSM)

44. Persistent Stored Modules (PSM)
A recent SQL standard

45. Persistent Stored Modules (PSM)
A recent SQL standard
Mechanism for user to store in the DB schema functions and procedures that can be used in SQL statements

46. Persistent Stored Modules (PSM)
A recent SQL standard
Mechanism for user to store in the DB schema functions and procedures that can be used in SQL statements
The functions and procedures are written in a simple general-purpose language

47. Persistent Stored Modules (PSM)
A recent SQL standard
Mechanism for user to store in the DB schema functions and procedures that can be used in SQL statements
The functions and procedures are written in a simple general-purpose language
Includes if, loop, variable declaration, as well as SQL queries and updates

48. Basic PSM Form

49. Basic PSM Form CREATE PROCEDURE <name> (<parameter list>)
<optional local declarations>
<body>;
CREATE FUNCTION <name> (<parameter list>) RETURNS <type>

50. Basic PSM Form CREATE PROCEDURE <name> (<parameter list>)
<optional local declarations>
<body>;
CREATE FUNCTION <name> (<parameter list>) RETURNS <type>
PSM uses mode-name-type triples for parameters, where the mode can be:
IN = procedure uses value, does not change value.
OUT = procedure changes, does not use.
INOUT = both.

51. Example: Stored Procedure
Let’s write a procedure that takes two arguments b and p, and adds a tuple to Sells(bar, beer, price) that has bar = ’Joe’’s Bar’, beer = b, and price = p. (can be used by Joe to add to his menu more easily.

52. Example: Stored Procedure
Let’s write a procedure that takes two arguments b and p, and adds a tuple to Sells(bar, beer, price) that has bar = ’Joe’’s Bar’, beer = b, and price = p. (can be used by Joe to add to his menu more easily.
CREATE PROCEDURE JoeMenu (
IN b CHAR(20),
IN p REAL )
INSERT INTO Sells
VALUES(’Joe’’s Bar’, b, p);

53. Example: Stored Procedure
Let’s write a procedure that takes two arguments b and p, and adds a tuple to Sells(bar, beer, price) that has bar = ’Joe’’s Bar’, beer = b, and price = p. (can be used by Joe to add to his menu more easily.
CREATE PROCEDURE JoeMenu (
IN b CHAR(20),
IN p REAL )
INSERT INTO Sells
VALUES(’Joe’’s Bar’, b, p);
Parameters are both
read-only, not changed

54. Example: Stored Procedure
Let’s write a procedure that takes two arguments b and p, and adds a tuple to Sells(bar, beer, price) that has bar = ’Joe’’s Bar’, beer = b, and price = p. (can be used by Joe to add to his menu more easily.
CREATE PROCEDURE JoeMenu (
IN b CHAR(20),
IN p REAL )
INSERT INTO Sells
VALUES(’Joe’’s Bar’, b, p);
Parameters are both
read-only, not changed
The body is a
single insertion

55. Invoking Procedures

56. Invoking Procedures
Use SQL/PSM statement CALL, with the name of the procedure and arguments.

57. CALL JoeMenu(’Moosedrool’, 5.00);
Invoking Procedures
Use SQL/PSM statement CALL, with the name of the procedure and arguments.
Example:
CALL JoeMenu(’Moosedrool’, 5.00);

58. CALL JoeMenu(’Moosedrool’, 5.00);
Invoking Procedures
Use SQL/PSM statement CALL, with the name of the procedure and arguments.
Example:
CALL JoeMenu(’Moosedrool’, 5.00);
Functions used in SQL expressions wherever a value of their return type is appropriate.

59. Types of PSM statements

60. Types of PSM statements
RETURN <expression> sets the return value of a function.

61. Types of PSM statements
RETURN <expression> sets the return value of a function.
DECLARE <name> <type> is used to declare local variables.

62. Types of PSM statements
RETURN <expression> sets the return value of a function.
DECLARE <name> <type> is used to declare local variables.
BEGIN END for groups of statements.
* Separate statements by semicolons.

63. Types of PSM statements
RETURN <expression> sets the return value of a function.
DECLARE <name> <type> is used to declare local variables.
BEGIN END for groups of statements.
* Separate statements by semicolons.
Assignment statements:
SET <variable> = <expression>;
Example: SET b = ’Bud’;

64. Types of PSM statements
RETURN <expression> sets the return value of a function.
DECLARE <name> <type> is used to declare local variables.
BEGIN END for groups of statements.
* Separate statements by semicolons.
Assignment statements:
SET <variable> = <expression>;
Example: SET b = ’Bud’;
Statement labels: give a statement a label by prefixing a name and a colon.

65. IF Statements

66. IF Statements Simplest form: IF <condition> THEN
END IF;

67. IF Statements Simplest form: IF <condition> THEN
END IF;
Add ELSE <statements> if desired:
IF THEN ELSE END IF;

68. IF Statements Simplest form: IF <condition> THEN
END IF;
Add ELSE <statements> if desired:
IF THEN ELSE END IF;
Add additional cases by
ELSEIF <statements>:
IF … THEN … ELSEIF … ELSEIF … ELSE … END IF;

69. Example: IF Statement

70. unpopular (<100), average (100-199), popular (200)
Example: IF Statement
Rate bars by the number of customers they have, based on Frequents(drinker,bar):
unpopular (<100), average ( ), popular (200)

71. unpopular (<100), average (100-199), popular (200)
Example: IF Statement
Rate bars by the number of customers they have, based on Frequents(drinker,bar):
unpopular (<100), average ( ), popular (200)
CREATE FUNCTION Rate (IN b CHAR(20) )
RETURNS CHAR(10)
DECLARE cust INTEGER;
BEGIN
SET cust = (SELECT COUNT(*) FROM Frequents
WHERE bar = b);
IF cust < 100 THEN RETURN ’unpopular’
ELSEIF cust < 200 THEN RETURN ’average’
ELSE RETURN ’popular’
END IF;
END;

72. unpopular (<100), average (100-199), popular (200)
Example: IF Statement
Rate bars by the number of customers they have, based on Frequents(drinker,bar):
unpopular (<100), average ( ), popular (200)
CREATE FUNCTION Rate (IN b CHAR(20) )
RETURNS CHAR(10)
DECLARE cust INTEGER;
BEGIN
SET cust = (SELECT COUNT(*) FROM Frequents
WHERE bar = b);
IF cust < 100 THEN RETURN ’unpopular’
ELSEIF cust < 200 THEN RETURN ’average’
ELSE RETURN ’popular’
END IF;
END;
number of
customers of bar b

73. unpopular (<100), average (100-199), popular (200)
Example: IF Statement
Rate bars by the number of customers they have, based on Frequents(drinker,bar):
unpopular (<100), average ( ), popular (200)
CREATE FUNCTION Rate (IN b CHAR(20) )
RETURNS CHAR(10)
DECLARE cust INTEGER;
BEGIN
SET cust = (SELECT COUNT(*) FROM Frequents
WHERE bar = b);
IF cust < 100 THEN RETURN ’unpopular’
ELSEIF cust < 200 THEN RETURN ’average’
ELSE RETURN ’popular’
END IF;
END;
number of
customers of bar b
nested IF
statement

74. unpopular (<100), average (100-199), popular (200)
Example: IF Statement
Rate bars by the number of customers they have, based on Frequents(drinker,bar):
unpopular (<100), average ( ), popular (200)
CREATE FUNCTION Rate (IN b CHAR(20) )
RETURNS CHAR(10)
DECLARE cust INTEGER;
BEGIN
SET cust = (SELECT COUNT(*) FROM Frequents
WHERE bar = b);
IF cust < 100 THEN RETURN ’unpopular’
ELSEIF cust < 200 THEN RETURN ’average’
ELSE RETURN ’popular’
END IF;
END;
number of
customers of bar b
return occurs
here, not at
one of the
RETURN
statements
nested IF
statement