1. Part2 The Relational Database Chapter 03- Structured Query Language (SQL)
Database Systems
Lu Wei
College of Software and Microelectronics
Northwestern Polytechnical University

2. Outline Introduction Basic SQL Setting Up and Using PostgreSQL
Advanced SQL
Embeded SQL
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3. Outline Introduction Basic SQL Setting Up and Using PostgreSQL
Advanced SQL
Embeded SQL
Lu Wei

4. Introduction What is SQL Objectives of SQL
SQL is abbreviation of Structured Query Language.
It is the way we access the database.
Objectives of SQL
Allow a user to
Create the database and relation structure.
Perform basic data management tasks. (Insertion, modification, and deletion of data from relation)
Perform both simple and complex queries
Perform these tasks with minimal user effort
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5. Introduction History of SQL
E.F.Codd – ‘A relational model of data for large shared data banks’ (1970)
1974, D.Chamberlin defined the Structured English Query Language (SEQUEL)
1976, a revised version SEQUEL/2 – SQL
IBM, System R based on SEQUEL/2
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6. Introduction
Late 1970s, the first commercial implementation of relational DBMS based on SQL – ORACLE
IBM, 1982, SQL/DS; 1983, DB2
1982, the American National Standards Institute began work on a Relational Database Language (RDL) based on a concept paper from IBM.
SQL-86, SQL-89, SQL-92(SQL2), SQL-99(SQL3)
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7. Introduction Features of SQL
Non-procedual - based on relational algebra and relational calculus
Easy to learn
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8. Introduction Importance of SQL
SQL is the first and, so far, only standard database language to gain wide acceptance.
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9. Introduction SQL can be used in two ways
Use SQL interactively by entering the statements at a terminal
Embed SQL statements in a procedural language (programmatic SQL)
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10. Outline Introduction Basic SQL Setting Up and Using PostgreSQL
Advanced SQL
Embeded SQL
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11. Basic SQL Writing SQL Commands Data Definition Language (DDL)
Data Manipulation Language (DML)
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12. Basic SQL Writing SQL Commands Data Definition Language (DDL)
Data Manipulation Language (DML)
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13. Writing SQL Commands
An SQL statement consists of reserved words and user-defined words.
Most components of an SQL statement are case insensitive.
Usually a statement terminator (;) is used to end each SQL statement. (Although the standard does not require it)
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14. Writing SQL Commands
Although SQL is free-format, an SQL statement or set of statements is more readable if indentation and lineation are used.
Each clause in a statement should begain on a new line;
The beginning of each clause should line up with the beginning of other clause;
If a clause has several parts, they should each appear on a separate line and be indented. …
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15. Writing SQL Commands
We use the extended form of the Backus Naur Form (BNF) notation to define SQL statement.
Uper-case letters represent reserved words;
Lower-case letters represent user-defined words;
A vertical bar(|) indicates a choice among alternatives;
Curly braces({}) indicate a required element;
Square brackets([]) indicate an optional element;
An ellipsis(…) indicate optional repetition of an item.
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16. Basic SQL Writing SQL Commands Data Definition Language (DDL)
Data Manipulation Language (DML)
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17. Data Definition Language (DDL)
The ISO SQL Data Types
Integrity Enhancement Feature (IEF)
Data Definition
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18. Data Definition Language (DDL)
The ISO SQL Data Types
Integrity Enhancement Feature (IEF)
Data Definition
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19. The ISO SQL Data Types SQL Identifiers
Used to identify objects in the database, such as table names, view names, and columns.
Character set
A…Z, a…z
0…9
Underscore(_)
Restrictions
An identifier can be no longer than 128 characters
An identifier must start with a letter
An identifier cannot contain spaces
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20. The ISO SQL Data Types
SQL Scalar Data Types
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21. The ISO SQL Data Types Examples branchNo CHAR(4) address VARCHAR(30)
rooms SMALLINT
salary DECIMAL(7,2)
viewDate DATE
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22. The ISO SQL Data Types Scalar operators +,-,*,/
LOWER,UPPER,TRIM,SUBSTRING
CURRENT_USER, SESSION_USER …
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23. Data Definition Language (DDL)
The ISO SQL Data Types
Integrity Enhancement Feature (IEF)
Data Definition
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24. Integrity Enhancement Feature (IEF)
NOT NULL Constraints
position VARCHAR(10) NOT NULL
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25. Integrity Enhancement Feature (IEF)
Domain Constraints
sex CHAR NOT NULL CHECK (sex IN(‘M’,’F’))
CREATE DOMAIN SexType AS CHAR
DEFAULT ‘M’
CHECK(VALUE IN(‘M’,’F’));
sex SexType NOT NULL
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26. CREATE DOMAIN DomainName [AS] dataType [DEFAULT defaultOption]
Domain definition
CREATE DOMAIN DomainName [AS] dataType
[DEFAULT defaultOption]
[CHECK(searchCondition)]
DROP DOMAIN DomainName [RESTRICT|CASCADE]
CREATE DOMAIN BranchNumber AS CHAR(4)
CHECK(VALUE IN(SELECT branchNo FROM Branch));
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27. Integrity Enhancement Feature (IEF)
Entity Integrity
The primary key of a table must contain a unique, non-null value for each row.
The PRIMARY KEY clause can be specified only once per table.
PRIMARY KEY (columnName[,columnName])
PRIMARY KEY (propertyNo)
PRIMARY KEY (sNo)
PRIMARY KEY (clientNo,propertyNo)
PRIMARY KEY (sNo,cNo)
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28. Integrity Enhancement Feature (IEF)
Alternate keys can be ensured uniqueness using the keyword UNIQUE.
Every column that appears in a UNIQUE clause must be declared as NOT NULL.
UNIQUE (columnName[,columnName])
UNIQUE (clientNo,propertyNo)
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29. Integrity Enhancement Feature (IEF)
Referential Integrity
Referential integrity is implemented through FOREIGN KEY.
A value in the foregin key must refer to an existing valid row in the parent table or be null.
Define the foreign key
FOREIGN KEY (columnName[,columnName])
REFERENCES TableName[(columnName[,columnName])]
[ON DELETE|UPDATE CASCADE|SET NULL|SET DEFAULT|NO ACTION]
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30. Integrity Enhancement Feature (IEF)
Exmples
FOREIGN KEY stuffNo
REFERENCES Staff ON DELETE SET NULL
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31. Integrity Enhancement Feature (IEF)
Enterprise Constraints
The CREATE ASSERTION statement is an integrity constaint that is not directly linked with a table definition.
CREATE ASSERTION AssertionName
CHECK (searchCondition)
CREATE ASSERTION StaffNotHandlingTooMuch
CHECK (NOT EXISTS (SELECT staffNo
FROM PropertyForRent
GROUP BY staffNo
HAVING COUNT(*)>100))
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32. Data Definition Language (DDL)
The ISO SQL Data Types
Integrity Enhancement Feature (IEF)
Data Definition
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33. Data Definition Creating a Database
The ISO standard does not specify how database are created, and each dialect generally has a different approach.
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34. Data Definition Creating a table (CREATE TABLE) CREATE TABLE TableName
{(columnName dataType [NOT NULL][UNIQUE]
[DEFAULT defaultOption][CHECK(searchCondition)][,…]}
[PRIMARY KEY (listOfColumns),]
{[UNIQUE (listOfColumns),][,…]}
{[FOREIGN KEY (listOfForeignKeyColumns)
REFERENCES ParentTableName[(listOfCandidateKeyColumns)],
[MATCH {PARTIAL|FULL}
[ON UPDATE referentialAction]
[ON DELETE referentialAction]][,…]}
{[CHECK(searchCondition)][,…]})
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35. Data Definition Student (sNo, sName, sSex, sAge, sDept)
Course (cNo, cName, cPNo, cCredit)
SC (sNo, cNo, score)
example1table.sql
Branch (branchNo, street, city, postcode)
Staff (staffNo, fName, lName, position, sex, DOB, salary, branchNo)
PropertyForRent (propertyNo, street, city, postcode, type, rooms, rent, ownerNo,
staffNo, branchNo)
Client (clientNo, fName, lName, telNo, prefType, maxRent)
PrivateOwner (ownerNo, fName, lName, address, telNo)
Viewing (clientNo, propertyNo, viewDate, comment)
Registration (clientNo, branchNo, staffNo, dateJoined)
example2table.sql
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36. Data Definition Changing a Table Definition (ALTER TABLE)
ALTER TABLE TableName
[ADD [COLUMN] columnName dataType [NOT NULL][UNIQUE]
[DEFAULT defaultOption][CHECK(searchCondition)]]
[DROP [COLUMN] columnName [RESTRICT|CASCADE]]
[ADD [CONSTRAINT [constraintName]] tableConstraintDefinition]
[DROP CONSTRAINT constraintName [RESTRICT|CASCADE]]
[ALTER [COLUMN] SET DEFAULT defaultOption]
[ALTER [COLUMN] DROP DEFAULT]
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37. Data Definition Examples ALTER TABLE Staff
ALTER position DROP DEFAULT;
ALTER TABLE Student
ALTER sSex SET DEFAULT ‘M’;
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38. Data Definition Removing a Table (DROP TABLE)
DROP TABLE TableName [RESTRICT|CASCADE]
DROP TABLE Student;
DROP TABLE Staff;
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39. Basic SQL Writing SQL Commands Data Definition Language (DDL)
Data Manipulation Language (DML)
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40. Data Manipulation Language (DML)
Query
Data Update
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41. Data Manipulation Language (DML)
Query
Data Update
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42. Query
General form
The purpose of the SELECT statement is to retrive and display data from one or more database tables.
It is capable of performing the equivalent of the relational algebra’s Selection, Projection, and Join operations in a single statement
SELECT [DISTINCT|ALL]{*|[columnExpression[AS newName]][,…]}
FROM TableName[alias][,…]
[WHERE condition]
[GROUP BY columnList][HAVING condition]
[ORDER BY columnList]
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43. Query SELECT A1 , A2 , ..., An FROM R1,R2,…,Rm WHERE F 
πA1,A2,...,An(σF(R1× R2×...×Rm))
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44. Query Retrieve all columns, all rows
SELECT staffNo,fName,position,sex,DOB,
salary,branchNo
FROM Staff;
SELECT *
FROM Staff;
SELECT *
FROM Student;
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45. Query Retrieve specific columns, all rows
SELECT staffNo,fName,lName,salary
FROM Staff;
SELECT sNo,sName
FROM Student;
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46. Query Use DISTINCT eliminate the duplicates
SELECT DISTINCT propertyNo FROM Viewing;
SELECT DISTINCT sNo FROM SC;
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47. Query Calculated fields SELECT staffNo,fName,lName,salary/12
FROM Staff;
SELECT sName, 2008-sAge
FROM Student;
SELECT staffNo,fName,lName,
salary/12 AS monthlySalary
FROM Staff;
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48. Query Row selection (WHERE clause)
Basic search conditions in WHERE clause
Condition
Predicates(谓词)
comparison
Comparison operators(=,>,<,<>,<=,>=,!=)
range
BETWEEN AND, NOT BETWEEN AND
set membership
IN, NOT IN
pattern match
LIKE, NOT LIKE
null
IS NULL, IS NOT NULL
logical operators
AND, OR,NOT
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49. Query
(1) comparison
SELECT staffNo,fName,lName,positon,salary FROM Staff
WHERE salary > 10000;
SELECT sName FROM Student
WHERE sDept = 'CS';
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50. Query
(2)range
SELECT staffNo,fName,lName,positon,salary FROM Staff WHERE salary BETWEEN AND 30000;
SELECT staffNo,fName,lName,positon,salary FROM Staff WHERE salary >= AND salary <= 30000;
SELECT sName, sDept, sAge FROM Student WHERE sAge NOT BETWEEN 20 AND 23;
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51. Query (3)set membership
SELECT staffNo,fName,lName, 　 FROM Staff 　 WHERE position IN (‘Manager',‘Supervisor');
SELECT staffNo,fName,lName, 　 FROM Staff 　 WHERE position = ‘Manager’
OR position = ‘Supervisor';
SELECT sName, sSex 　 FROM Student 　 WHERE sDept NOT IN ('IS', 'MA', 'CS');
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52. Query
(4)pattern match
%--represents any sequence of zero or more characters (wildcard)
_--represents any single character
Escape character--\,#
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53. Query SELECT clientNo,fName,lName,address,telNo
FROM PrivateOwner WHERE address LIKE ‘%Glasgow%’;
SELECT sName, sNo, sSex FROM Student WHERE sName LIKE ‘刘%’;
查询以”DB_”开头，且倒数第三个字符为i的课程的详细情况
SELECT *
FROM Course
WHERE cName LIKE ’DB\_%i__’ ESCAPE ’\’;
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54. Query
(5)null
List the details of all viewings on property PG4 where a comment has not been supplied
SELECT clientNo,viewDate 　 FROM Viewing WHERE propertyNo = ‘PG4’ AND comment = ‘’;
SELECT clientNo,viewDate 　 FROM Viewing WHERE propertyNo = ‘PG4’ AND comment IS NULL;
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55. Query (6)logical operators
SELECT sName FROM Student WHERE sDept='CS' AND Sage<20;
SELECT * FROM Branch WHERE city=‘London' OR city=‘Glasgow’;
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56. Query Sorting Results (ORDER BY clause)
In general, the rows of an SQL query result table are not arranged in any particular order. We can user ORDER BY clause in the SELECT statement to sort the results.
The ORDER BY clause must always be the last clause of the SELECT statement.
ASC—ascending order, default order
DESC—descending order
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57. Query Examples SELECT staffNo,fName,lName,salary FROM Staff
ORDER BY salary DESC;
ORDER BY 4 DESC
SELECT sNo, score
FROM SC
WHERE cNo=‘001' ORDER BY score DESC;
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58. Query
SELECT propertyNo,type,rooms,rent FROM PropertyForRent ORDER BY type,rent DESC;
SELECT * FROM Student ORDER BY sDept, sAge DESC;
Which is the place for null?
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59. Query Using the SQL Aggregate Functions
The ISO standard defines five aggregate functions
COUNT([DISTINCT|ALL] *)
COUNT([DISTINCT|ALL] <columnName>)
SUM([DISTINCT|ALL] <columnName>) AVG([DISTINCT|ALL] < columnName >)
MAX([DISTINCT|ALL] < columnName >) MIN([DISTINCT|ALL] < columnName >)
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60. Query
COUNT, MIN, and MAX apply to both numeric and non-numeric fields, but SUM and AVG may be used on numeric field only.
Apart from COUNT(*), each function eliminates nulls first and operates only on the remaining non-null values.
Aggregate functions can be used only in the SELECT list and in the HAVING clause.
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61. Query SELECT COUNT(*) FROM Student;
SELECT COUNT(*) AS my_count FROM PropertyForRent
WHERE rent > 350;
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62. Query SELECT COUNT(DISTINCT propertyNo) AS mycount FROM Viewing
WHERE viewDate BETWEEN ’01-May-08’
AND ‘31-May-08’;
SELECT COUNT(DISTINCT sNo)
FROM SC;
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63. Query Find the total number of Managers and the sum of their salaries
SELECT COUNT(staffNo) AS my_count,
SUM(salary) AS my_sum FROM Staff
WHERE position = ‘Manager’;
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64. Query SELECT AVG(score) FROM SC WHERE Cno='1';
SELECT MAX(score) FROM SC WHERE cNo='1';
SELECT MIN(salary),MAX(salary),
AVG(salary) FROM Staff;
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65. Query Grouping Results (GROUP BY clause)
All column names in the SELECT list must appear in the GROUP BY clause unless the name is used only in an aggregate function.
When the WHERE clause is used with GROUP BY, the WHERE clause is applied first.
The ISO standard considers two nulls to be equal for purposes of the GROUP BY clause.
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66. Query
Find the number of staff working in each branch and the sum of their salaries.
SELECT branchNo,COUNT(staffNo),SUM(salary)
FROM Staff
GROUP BY branchNo
ORDER BY branchNo;
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67. Query SELECT branchNo,(SELECT COUNT(staffNo) FROM Staff s
WHERE s.branchNo=b.branchNo),
(SELECT SUM(salary)
WHERE s.branchNo=b.branchNo)
FROM Branch b
ORDER BY branchNo;
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68. Query Restricting groupings (HAVING clause)
HAVING clause is designed for use with the GROUP BY clause to restrict the groups that appear in the final result table.
Similar in syntax, HAVING and WHERE serve different purposes.
The ISO standard requires that column names used in the HAVING clause must also appear in the GROUP BY list or be contained within an aggregate function.
The HAVING clause is not a necessary part of SQL.
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69. Query SELECT branchNo,COUNT(staffNo),SUM(salary) FROM Staff
GROUP BY branchNo
HAVING COUNT（staffNo）> 1
ORDER BY branchNo;
SELECT sNo
FROM SC
WHERE score>60
GROUP BY sNo
HAVING COUNT(*)>3;
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70. Query
Subqueries
In SQL statement, a SELECT-FROM-WHERE statement is called a query block.
A query block embedded within WHERE or HAVING clause of another query block is called a subquery or nested query.
Subqueries may also appear in INSERT, UPDATE, and DELETE statements.
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71. Query There three types of subquery
A scalar subquery returns a single column and single row.
A row subquery returns multiple columns, but again only a single row.
A table subquery returns one or more columns and multiple rows.
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72. Query (1) use of IN predicate
List the students who study in the same department as ‘刘晨’
SELECT sDept FROM Student WHERE sName=‘刘晨’;
Suppose the result is ‘IS’
SELECT sNo, sName, sDept FROM Student WHERE sDept='IS';
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73. Query
SELECT sNo, sName, sDept FROM Student WHERE sDept IN 　     （SELECT sDept       FROM Student       WHERE sName=‘刘晨’）;
SELECT sNo, sName, sDept FROM Student S1, Student S2 WHERE S1.sDept = S2.sDept AND S2.sName =‘刘晨‘;
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74. Query List the students who elect the course ‘IS’
SELECT sNo, sName FROM Student WHERE sNo IN       SELECT sNo       FROM SC       WHERE cNo IN           （SELECT cNo             FROM Course             WHERE cName=‘IS’）;
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75. Query
SELECT sNo, sName FROM Student, SC, Course WHERE Student.sNo=SC.sNo AND
SC.cNo=Course.cNo AND
Course.cName=‘IS’;
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76. Query
List the properties that are handled by staff who work in the branch at ‘163 Main St’
SELECT propertyNo,street,city,type,rooms FROM PropertyForRent WHERE staffNo IN      (SELECT staffNo       FROM Staff       WHERE branchNo IN           (SELECT branchNo            FROM Branch            WHERE street=‘163 Main St’));
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77. Query
For all the subqueries we discuss above, each subquery executes only once and the result of the subquery is used by supquery. The condition of subquery is not dependent on the condition of supquery. We call this type of query independent query.
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78. Query (2) use of comparison operators in subquery
The subquery must place after the comparison operator.
The subquery SELECT list must consist of a single column name or expression, except for subqueries that use the keyword EXISTS.
The ORDERBYclause may not be used in a subquery.
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79. Query
List the students who study in the same department as ‘刘晨’. We can rewrite the query as follow:
SELECT sNo, sName, sDept FROM Student WHERE sDept ＝ 　     （SELECT sDept       FROM Student       WHERE sName=‘刘晨’）;
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80. Query
SELECT sNo, sName, sDept FROM Student WHERE (SELECT sDept             FROM Student             WHERE sName='刘晨') = sDept;
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81. Query
List the students who elect the course ‘IS’. Can we rewrite the query as folow?
SELECT sNo, sName FROM Student WHERE sNo       SELECT sNo       FROM SC       WHERE cNo             SELECT cNo             FROM Course             WHERE cName=‘IS’ ； IN = IN =
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82. Query
Can we use the ‘=’ replace the predicate ‘IN’ in the follow example we discuss above?
SELECT propertyNo,street,city,type,rooms FROM PropertyForRent WHERE staffNo IN      (SELECT staffNo       FROM Staff       WHERE branchNo IN           (SELECT branchNo            FROM Branch            WHERE street=‘163 Main St’));
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83. Query (3) use aggregate function in subquery
List all staff whose salary is greater than the average salary, and show by how much their salary is greater than the average.
SELECT staffNo,fName,lName,
salary-(SELECT AVG(salary)
FROM Staff) AS salDiff FROM Staff WHERE salary > (SELECT AVG(salary)
FROM Staff)；
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84. Query (4)use ANY/ SOME and ALL in subquery
>ANY, <ANY, >=ANY, <=ANY, =ANY, <>ANY/!=ANY
>ALL, <ALL, >=ALL, <=ALL, =ALL(no meaning), <>ALL/!=ALL
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85. Query
List the student who is not in department ‘IS’ and their age less then any student in department ‘IS’. Sort the result according to age in descending order.
SELECT sName, sAge FROM Student WHERE sAge < ANY (SELECT sAge       FROM Student       WHERE sDept=‘IS’ )   AND sDept <> 'IS' ORDER BY sAge DESC;
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86. Query
SELECT sName, sAge FROM Student WHERE sAge <       (SELECT MAX(sAge)         FROM Student         WHERE sDept='IS') AND sDept <> 'IS' ORDER BY sAge DESC;
when using aggregate function to implement the query, usually the efficience is higher than using ANY or ALL
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87. Query
List the student who is not in department ‘IS’ and their age less then all student in department ‘IS’. Sort the result according to age in descending order.
SELECT sName, sAge FROM Student WHERE sAge<ALL (SELECT sAge       FROM Student       WHERE sDept=‘IS’ )   AND sDept <> 'IS' ORDER BY sAge DESC;
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88. Query
SELECT sName, sAge FROM Student WHERE sAge <       (SELECT MIN(sAge)         FROM Student         WHERE sDept='IS') AND sDept <> 'IS' ORDER BY sAge DESC;
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89. Query
Find all staff whose salary is largeer than the salary of at least one member of staff at branch ‘B003’
SELECT staffNo,fName,lName,position,salary FROM Staff WHERE salary > SOME(SELECT salary       FROM Staff       WHERE branchNo=‘B003’);
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90. Query
Find all staff whose salary is largeer than the salary of every member of staff at branch ‘B003’
SELECT staffNo,fName,lName,position,salary FROM Staff WHERE salary > ALL(SELECT salary       FROM Staff       WHERE branchNo=‘B003’);
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91. Query
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92. Query Muti-Table Queries
To combine columns from several tables into a result table we need to use a join operation.
To obtain information from more than one table, the choice is between using a subquery and using a join.
If the final result table is to contain columns from different tables, then we must use a join.
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93. Query (1) equijoin and non-equijoin
List all students and the courses they elect.
SELECT Student.*, SC.* FROM Student, SC WHERE Student.sNo=SC.sNo;
SELECT Student.sNo, sName, sSex, sAge, sDept, cNo, score
FROM Student, SC
WHERE Student.sNo=SC.sNo;
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94. Query
List the names of all clients who have viewed a property along with any comment supplied.
SELECT c.clientNo,fName,lName,
propertyNo,comment FROM Client c,Viewing v WHERE c.clientNo = v.clientNo;
Note: When Cartesian product appear?
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95. Query
(2) self-join
List the interval prerequest courses of all courses.
查询每门课的间接选修课（即先修课的先修课）
SELECT FIRST.cNo, SECOND.cPNo FROM Course FIRST, Course SECOND WHERE FIRST.cPNo=SECOND.cNo;
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96. Query (3) outer join sNo sName sAge s1 … s2 s3 sNo cNo score s1 c1 …
List all students along with their elective courses even the student have not elect any course.
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97. Query branchNo bCity B003 Glasgow B004 Bristol B002 London propertyNo
PropertyForRent1
branchNo
bCity
B003
Glasgow
B004
Bristol
B002
London
propertyNo
pCity
PA14
Aberdeen
PL94
London
PG4
Glasgow
List the branch offices and properties that are in the same city along with any unmatched branches.
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98. Query SELECT s.*, sc.* FROM Student s, SC sc WHERE s.sNo = sc.sNo;
SELECT b.*, p.* FROM Branch1 b, PropertyForRent1 p WHERE b.bCity = p.pCity;
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99. Query There three types of Outer join: Left outer join
Right outer join
Full outer join
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100. Query
List all students along with their elective courses even the student have not elect any course.
SELECT s.*, sc.* FROM Student s LEFT JOIN SC sc ON s.sNo = sc.sNo;
SELECT s.*, sc.* FROM Student s, SC sc WHERE s.sNo = sc.sNo(*);
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101. Query
List the branch offices and properties that are in the same city along with any unmatched branches.
SELECT b.*,p.* FROM Branch1 b LEFT JOIN PropertyForRent1 p ON b.bCity = p.pCity;
SELECT b.*,p.* FROM Branch1 b,PropertyForRent1 p WHERE b.bCity = p.pCity(*);
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102. Query
SELECT s.*, sc.* FROM Student s RIGHT JOIN SC sc ON s.sNo = sc.sNo;
SELECT b.*,p.* FROM Branch1 b RIGHT JOIN PropertyForRent1 p ON b.bCity = p.pCity;
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103. Query
SELECT s.*, sc.* FROM Student s FULL JOIN SC sc ON s.sNo = sc.sNo;
SELECT b.*,p.* FROM Branch1 b FULL JOIN PropertyForRent1 p ON b.bCity = p.pCity;
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104. Query Muti-table join SELECT b.branchNo,b.city,s.staffNo,fName,
lName,propertyNo FROM Branch b,Staff s,PropertyForRent p WHERE b.branchNo = s.branchNo
AND s.staffNo = p.staffNo
ORDER BY b.branchNo,s.staffNo,propertyNo;
FROM (Branch b JOIN Staff s USING branchNo) AS bs JOIN PropertyForRent p USING staffNo;
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105. Query ISO SQL syntax SELECT table1.column,tabel2.column FROM talbe1
[CROSS JOIN table2] |
[NATURAL JOIN table2] |
[JOIN table2 USING(column_name)] |
[JOIN table2
ON(table1.column_name=table2.column_name)] |
[LEFT|RIGHT|FULL OUTER JOIN table2
ON(table1.column_name=table2.column_name)];
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106. Query EXISTS and NOT EXISTS
EXISTS and NOT EXISTS is existential quantifiers. They produce a simple true/false result.
Since EXISTS and NOT EXISTS check only for the existence or non-existence of rows in the subquery result table, the subquery can contain any number of columns.
Usually we write the subquery as: (SELECT * FROM…)
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107. Query Examples List the students who have not elected course ‘001’
SELECT sName FROM Student WHERE NOT EXISTS       (SELECT *         FROM SC         WHERE sNo=Student.sNo AND cNo=‘001');
Can we use NOT IN to implement this query?
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108. Query Find all staff who work in a London branch office
SELECT staffNo,fName,lName,postion FROM Staff s WHERE EXISTS       (SELECT *         FROM Branch b         WHERE s.branchNo = b.branchNO
AND city =‘Lodon');
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109. Query
SELECT staffNo,fName,lName,postion FROM Staff s, Branch b WHERE s.branchNo = b.branchNO
AND city =‘Lodon');
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110. Query
Some subqueries using EXISTS or NOT EXISTS can be replace by subqueries with other form (IN etc.), but some can’t.
Examples
List the students who study in the same department as ‘刘晨’. (refer to page73)
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111. Query
SELECT sNo, sName, sDept FROM Student S1 WHERE EXISTS 　       SELECT *       FROM Student S2       WHERE S2.sDept=S1.sDept AND
S2.sName='刘晨';
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112. Query (x)P  ┐(x(┐P))
There is no direct expression for universal quantifier(全称量词) in SQL. We can use predication calculus to transform a predication using universal quantifiers to a predication using existential quantifiers.
(x)P  ┐(x(┐P))
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113. Query List the students who elect all courses.
SELECT sName FROM Student S WHERE NOT EXISTS       (SELECT *         FROM Course C         WHERE NOT EXISTS               (SELECT *                 FROM SC                 WHERE sNo=S.Sno AND
cNo=C.cNo);
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114. Query
There is also no direct expression for implication(全称量词) in SQL. We can also tranform it to expression using existential quantifiers.
p  q  ┐p ∨ q
(y)pq  ┐(y(┐(Pq)))
 ┐(y(┐(┐P∨q))  ┐y(P∧┐q)
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115. Query
List the students who elect the courses elected by ‘xxx’at least .
SELECT DISTINCT sNo FROM SC SCX WHERE NOT EXISTS        (SELECT *         FROM SC SCY         WHERE SCY.sNo=‘xxx' AND             NOT EXISTS                  (SELECT *                    FROM SC SCZ                    WHERE SCZ.sNo=SCX.sNo
AND SCZ.cNo=SCY.cNo);
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116. Query Combining Result Tables (UNION, INTERSECT, EXCEPT)
In SQL, we can use the normal set operations of Union, Intersection, and Difference to combine the results of two or more queries into a single result table.
The three set operators in the ISO standard are called UNION, INTERSECT, and EXCEPT
Operator[ALL][CORRESPONDING [BY{column1[,…]}]]
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117. Query
Examples
List the students who have elected course ‘001’ or ‘002’
(SELECT sNo FROM SC WHERE cNo=‘001‘) UNION (SELECT sNo FROM SC WHERE cNo=‘002‘);
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118. Query
List all cities where there is either a branch office or a property
(SELECT city FROM Branch WHERE city IS NOT NULL) UNION (SELECT city FROM PropertyForRent WHERE city IS NOT NULL);
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119. Query
(SELECT * FROM Branch WHERE city IS NOT NULL) UNION CORRESPONDING BY city (SELECT * FROM PropertyForRent WHERE city IS NOT NULL);
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120. Query List the students who have elected course ‘001’ and ‘002’
(SELECT sNo FROM SC WHERE cNo=‘001‘) INTERSECT (SELECT sNo FROM SC WHERE cNo=‘002‘);
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121. Query
SELECT sNo FROM SC WHERE cNo=‘001' AND       sNo IN          (SELECT sNo           FROM SC           WHERE cNo='2');
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122. Query
Construct a list of all cities where there is both a branch office and a property
(SELECT city FROM Branch) (INTERSECT SELECT city FROM PropertyForRent);
(SELECT * FROM Branch) INTERSECT CORRESPONDING BY city (SELECT * FROM PropertyForRent);
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123. Query SELECT DISTINCT b.city FROM Branch b,PropertyForRent p
WHERE b.city = p.city;
SELECT DISTINCT b.city FROM Branch b
WHERE EXISTS(SELECT *
FROM PropertyForRent p
WHERE b.city = p.city);
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124. Query
List the students who have elected course ‘001’ but have not elected course ‘002’
(SELECT sNo FROM SC WHERE cNo='1‘) EXCEPT (SELECT sNo FROM SC WHERE cNo='2‘);
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125. Query
SELECT sNo FROM SC WHERE cNo='1' AND       sNo NOT IN          (SELECT sNo           FROM SC           WHERE cNo='2');
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126. Query
Construct a list of all cities where there is a branch office but no properties.
(SELECT city FROM Branch) EXCEPT (SELECT city FROM PropertyForRent);
(SELECT * FROM Branch) EXCEPT CORRESPONDING BY city (SELECT city FROM PropertyForRent);
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127. Query SELECT DISTINCT city FROM Branch WHERE city NOT IN(SELECT city
FROM PropertyForRent);
SELECT DISTINCT city FROM Branch b WHERE NOT EXISTS
(SELECT *
FROM PropertyForRent p
WHERE b.city = p.city);
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128. Query …
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129. Data Manipulation Language (DML)
Query
Data Update
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130. Data Update Adding data to the database (INSERT)
Adds new rows of data to a table.
There are two forms of INSERT statement. The first allows a single row to be inserted into a named talbe and has the following format:
INSERT INTO TableName [(columnList)]
VALUES (data ValueList)
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131. Data Update
The second form of the INSERT statement allows multiple rows to be copied from one or more tables to another, and has the following format:
INSERT INTO TableName [(columnList)]
SELECT …
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132. Data Update
Examples
INSERT INTO Student VALUES (‘08020', '陈冬', '男', 18, 'IS' );
INSERT INTO SC(sNo, cNo) VALUES (‘08020', '1');
INSERT INTO Staff VALUES (‘SG44',‘Anne',‘Jones',‘Assistant', NULL,NULL,8100,’B003’);
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133. Data Update CREATE TABLE DeptAge (sDept CHAR(15), avgage SMALLINT);
INSERT INTO DeptAge(sDept, avgage)      (SELECT sDept, AVG(sAge)       FROM Student GROUP BY sDept);
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134. Data Update
Assume that there is a table StaffPropCount that contains the names of staff and the number of properties they manage:
StaffPropCount(staffNo,fName,lName,propCount)
We can popolate the StaffPropCount table using details from the Staff and PropertyForRent tables.
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135. Data Update
INSERT INTO StaffPropCount (SELECT s.staffNo,fName,lName,COUNT(*)
 FROM Staff s,PropertyForRent p
WHERE s.staffNo = p.staffNo
GROUP BY s.staffNo,s.fName,lName)
UNION
(SELECT staffNo,fName,lName,0
FROM Staff
WHERE staffNo NOT IN(SELECT DISTINCT staffNo
FROM PropertyForRent));
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136. Data Update Modifying data in the database (UPDATE)
Modifies existing data in a table.
UPDATE TableName
SET columnName1=dataValue1[,columnName2=datavalue2…]
[WHERE searchCondition]
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137. Data Update Examples UPDATE Student SET sAge=22 WHERE Sno=‘06001’;
UPDATE Staff SET salary = salary*1.05 WHERE position = ‘Manager’;
UPDATE Staff SET positon = ‘Manager’,salary = WHERE staffNo = ‘SG14’;
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138. Data Update UPDATE Student SET sAge=sAge+1;
UPDATE Staff SET salary = salary*1.03;
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139. Data Update UPDATE SC SET score=0 WHERE ‘CS’= (SELECT sDept
FROM Student
WHERE Student.sNo=SC.sNo);
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140. Data Update About consistency of update operation
UPDATE Student SET sNo=‘06089' WHERE Sno=‘07007';
UPDATE SC SET sNo=‘06089' WHERE sNo=‘07007';
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141. Data Update Deleting data from the database (DELETE)
Removes rows of data from a table
DELETE FROM TableName
[WHERE searchCondition]
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142. Data Update DELETE FROM Student WHERE sNo=‘05019'; DELETE FROM Viewing
WHERE propertyNo = ‘PG4';
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143. Data Update DELETE FROM SC; DELETE FROM Viewing;
DELETE FROM SC WHERE 'CS'=       (SELETE sDept        FROM Student        WHERE Student.sNo=SC.sNo);
We should enccounter the same problem about consistency.
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144. Data Update …
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145. Summary In this part you should have learned: What is SQL
How to write basic SQL statement
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146. Outline Introduction Basic SQL Setting Up and Using PostgreSQL
Advanced SQL
Embeded SQL
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147. Outline Introduction Basic SQL Setting Up and Using PostgreSQL
Advanced SQL
Embeded SQL
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148. Outline Introduction Basic SQL Setting Up and Using PostgreSQL
Advanced SQL
Embeded SQL
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149. Summary
In this chapter you should have learned:
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