Lecture 07 - Basic SQL

Trinity College

Basic SQL
Timothy Richards

Trinity College, Hartford CT • Department of Computer Science • CPSC 372

SQL Language
• Standard for Relational DBs
• Enabled success
• Easy to migrate
• From one DBMS to another
• SQL is the “same”
• In practice...
• Differences between relational DBMSs do exist!
• However, using those features that are part of the standard
makes migration easier.

Trinity College, Hartford CT • Department of Computer Science • CPSC 372 2

SQL Language
• Declarative Language


SQL Language
A user only speciﬁes what the result is to be...


SQL Language

The database ﬁgures out how to retrieve the result!


SQL Language

The database ﬁgures out how to retrieve the result!

This allows for greater ﬂexibility in the language
and more opportunity for an SQL compiler
to optimize queries to achieve increased performance!


SQL Language
• SQL: Structured Query Language
• Originally called SEQUEL
• Structured English Query Language
• Designed/Implemented at IBM Research for an
experimental DBMS called System R.

• SQL is now a standard
• American National Standards Institute (ANSI)
• International Standards Organization (ISO)


SQL Language
• Standards
• SQL-86 (SQL1)
• SQL-92 (SQL2)
• SQL:1999 (SQL3)
• SQL:2003 and SQL:2006 (XML support)
• SQL:2008 added object database features
• Later Standards
• Core speciﬁcation
• Plus Extensions (Optional)

SQL Language
• Comprehensive DB Language
• Data Deﬁnition Statements
• Updates Statements (Insert, Update, Delete)
• Query Statements
• Both DDL and DML
• Data Deﬁnition Language
• Data Manipulation Language
• SQL is Important and Large

SQL Language
• Comprehensive DB Language
• Data Deﬁnition Statements
• Updates Statements (Insert, Update, Delete)
• Query Statements
We’ll start with the
• Both DDL and DML basic DDL and DML
• Data Deﬁnition Language statements
• Data Manipulation Language
• SQL is Important and Large

Create Schema
• A Schema Elements
• Tables, Constraints,Views, Domains, and more!
• Identiﬁes By:
• A schema name
• An authorization identiﬁer

CREATE SCHEMA COMPANY AUTHORIZATION ‘trichards’;


Catalogs
• Catalog:
• A named collection of schemas in an SQL environment.
• An SQL environment is an installation of an SQL-
compliant RDBMS on a computer system.


Create Table
• Create Table Command
• Speciﬁes a new relation
• With a given name
• And a set of attributes
• Attributes are given names, types, and constraints


Create Table
CREATE TABLE COMPANY.EMPLOYEE (
Fname VARCHAR(15) NOT NULL,
Lname VARCHAR(15) NOT NULL,
Ssn CHAR(9) NOT NULL,
Bdate DATE,
Dno INT NOT NULL,
PRIMARY KEY (Ssn),
FOREIGN KEY (Dno) REFERENCES DEPT(no)
);


Create Table
CREATE TABLE COMPANY.EMPLOYEE (
Bdate DATE,
Dno INT NOT NULL,
PRIMARY KEY (Ssn),
);
Not Required


Create Table
CREATE TABLE COMPANY (
Bdate DATE,
Dno INT NOT NULL,
PRIMARY KEY (Ssn),
);
As long as you create the table
within the schema environment.


Create Table
Bdate DATE,
Dno INT NOT NULL,
PRIMARY KEY (Ssn),
);
Base command for creating a table


Create Table
Bdate DATE,
Dno INT NOT NULL,
PRIMARY KEY (Ssn),
);
Non-null Constraints


Create Table
Bdate DATE,
Dno INT NOT NULL,
PRIMARY KEY (Ssn),
);
Primary Key Constraint
entity integrity constraint
(non-null primary key)

Create Table
Bdate DATE,
Dno INT NOT NULL,
PRIMARY KEY (Ssn),
);
Foreign Key Constraint
referential integrity constraint
(non-null foreign key)

Attribute Domains
• Data Types
• Numeric
• Character string
• Bit string
• Boolean
• Time


Attribute Domains
• Data Types Integer (Int)
SmallInteger
• Numeric Float
• Character string Real
• Bit string Double
Decimal(i,j) (j is precision)
• Boolean
• Time


Attribute Domains
• Data Types Char(n)
• Numeric Varchar(n)
• Character string Clob
• Bit string
• Boolean
• Time


Attribute Domains
• Data Types Char(n) Fixed-length
• Numeric Varchar(n) Padded if string
is shorter than n
• Bit string
• Boolean
• Time


Attribute Domains
• Data Types Char(n) Variable-length
• Numeric Varchar(n) No Padding
• Bit string
• Boolean
• Time


Attribute Domains
• Data Types Char(n) Character
• Numeric Varchar(n) Large
• Character string Clob Object
Large text values
• Bit string such as documents
• Boolean
Maximum length
• Time speciﬁed as K, M,
or G.


Attribute Domains
• Data Types Char(n)
• Numeric Varchar(n)
• Bit string
Format
• Boolean ‘Smith’
• Time Concatenation
‘Bob ’ || ‘Smith’
‘Bob Smith’


Attribute Domains
• Data Types
• Numeric
• Character string Bit(n)
• Bit string Bit Varying(n)
• Boolean Blob
• Time


Attribute Domains
• Data Types
• Numeric
• Character string Bit(n) Fixed Length
• Bit string Bit Varying(n)
• Boolean Blob
• Time


Attribute Domains
• Data Types
• Numeric
• Character string Bit(n) Variable
• Bit string Bit Varying(n) Length
• Boolean Blob
• Time


Attribute Domains
• Data Types
• Numeric
• Character string Bit(n) Binary
• Bit string Bit Varying(n) Large
Object
• Boolean Blob
Images, Objects
• Time Max Size
as K, M, G:

Blob(30G)


Attribute Domains
• Data Types
• Numeric
• Character string Bit(n) Format
• Bit string Bit Varying(n) ‘B0010110’
• Boolean Blob
• Time


Attribute Domains
• Data Types
• Numeric
• Character string Format
• Bit string TRUE
FALSE
• Boolean Boolean
NULL (Unknow)
• Time three-valued logic


Attribute Domains
• Data Types
• Numeric
• Bit string
• Boolean
• Time Date
Time


Attribute Domains
• Data Types
• Numeric
• Bit string
• Boolean
• Time Date Format
Time YYYY-MM-DD
DATE‘2010-09-30’


Attribute Domains
• Data Types
• Numeric
• Bit string
• Boolean
• Time Date Format
Time HH:MM:SS
TIME’13:30:27’


Attribute Domains
• Data Types
• Numeric
Format
• Character string DATE TIME
• Bit string TIMESTAMP’2010-09-30 13:30:27’

• Boolean
• Time Date
Time
Timestamp

Extension Type

Attribute Domains
• Data Types
• Numeric Create your own domain!
• Character string CREATE DOMAIN SSN_TYPE AS CHAR(9);
• Bit string
• Boolean
• Time


Attribute Constraints
• Default
• Speciﬁes a default value for an attribute
Dno INT DEFAULT 75


• Default
Dno INT DEFAULT 75

• Check
• Impose a restriction on values
Dno INT NOT NULL CHECK (Dno > 0 AND Dno < 100)


• Default
Dno INT DEFAULT 75

• Check
• Impose a restriction on values
Dno INT NOT NULL CHECK (Dno > 0 AND Dno < 100)

• Key Constraint
PRIMARY KEY (Dno)
Dno INT PRIMARY KEY


• Unique
• Indicates uniqueness, but not a primary key
Dname Varchar(15) UNIQUE


• Unique
• Indicates uniqueness, but not a primary key
Dname Varchar(15) UNIQUE

Other constraints can be speciﬁed,
but often they depend on the RDBMS.


Retrieval Queries
SELECT-FROM-WHERE Structure

SELECT <attribute list>
FROM <table list>
WHERE <condition>;


Query Example
Retrieve the birth date and address of the
employee(s) whose name is ‘John B. Smith’

FROM <table list>
WHERE <condition>;


Query Example

SELECT Bdate, Address
FROM <table list>
WHERE <condition>;


Query Example

FROM EMPLOYEE
WHERE <condition>;


Query Example

FROM EMPLOYEE
WHERE Fname=‘John’ AND
Minit=’B’ AND
Lname=‘Smith’;


Query Example
Retrieve the name and address of all
employees who work for the ‘Research’ department.

FROM <table list>
WHERE <condition>;

What is different about this query?


Query Example

SELECT Fname, Lname, Address
FROM EMPLOYEE, DEPARTMENT
WHERE Dname=‘Research’ AND
Dnumber=Dno;



Query Example

SELECT Fname, Lname, Address
FROM EMPLOYEE, DEPARTMENT
WHERE Dname=‘Research’ AND
Dnumber=Dno;

It uses a join condition


Query Example
For every project located in ‘Stafford’, list the
project number, the controlling department number,
and the department manager’s last name, address,
and birth date.

FROM <table list>
WHERE <condition>;


Query Example
and birth date.

FROM <table list>
WHERE <condition>;


Query Example
and birth date.

SELECT Pnumber, Dnum,
Lname, Address,
Bdate
FROM PROJECT, DEPARTMENT,
EMPLOYEE
WHERE Dnum=Dnumber AND
Mgr_ssn=Ssn AND
Plocation=‘Stafford’;


Lecture 07 - Basic SQL

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