1 The Oracle Database System Building a Database Database Course The Hebrew University of Jerusalem

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The Oracle Database System

Building a Database

Database CourseThe Hebrew University of Jerusalem

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Technical Basics

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Connecting to the Database

At the command line prompt, write:

sqlplus login/password@stud.cs

In the beginning your password is the same as your login. You can change your password with the command:

password

To disconnect use the command:quit

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Connecting to the Database

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Running SQL Files

Instead of typing SQL commands into the SQLPLUS terminal, you can load commands from a file Use the command @file from SQLPLUS to load

the file file.sql Invoke the SQLPLUS command with the extra

parameter @file to load the file at connection: sqlplus login/password@stud.cs @file

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Spooling the Output

Output can be placed in a file: spool myFile.out

Spooling can be turned off with: spool off

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Tables Creation

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Creating a Table

The basic format of the CREATE TABLE command is:

CREATE TABLE TableName(Column1 DataType1 ColConstraint, …ColumnN DataTypeN ColConstraint,TableConstraint1, …TableConstraintM

);

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An Example

If you issue the command describe Cars you get:

Name Null? Type

-------- ----- ------------

LICENSE NUMBER

COLOR VARCHAR2(15)

CREATE TABLE Cars(License NUMBER,Color VARCHAR2(15));

Note that the definition is case insensitive

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Data Types

CHAR(n) String of length n (n <= 2000)

VARCHAR2(n) Variable length string of size <= n

(n <= 4000)

DATE Valid dates

CLOB Character large object (<= 4Gb)

NUMBER Up to 40 digits

NUMBER(n) Number of size n

NUMBER(n,m) Number of size n with m digits after decimal place

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Constraints in Create Table

Adding constraints to a table enables the database system to enforce data integrity.

However, adding constraints also makes inserting data slower.

• Different types of constraints:* Not Null * Default Values* Unique * Primary Key* Foreign Key * Check Condition

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Not Null Constraint

CREATE TABLE Employee(SSN NUMBER NOT NULL,Fname VARCHAR2(20),Lname VARCHAR2(20),Gender CHAR(1),Salary NUMBER(5) NOT NULL,Dept NUMBER

);

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Default Values

CREATE TABLE Employee(SSN NUMBER NOT NULL,Fname VARCHAR2(20),Lname VARCHAR2(20),Gender CHAR(1) DEFAULT(‘F’),Salary NUMBER(5) NOT NULL,Dept NUMBER

);

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CREATE TABLE Employee(SSN NUMBER UNIQUE NOT NULL,Fname VARCHAR2(20),Lname VARCHAR2(20),Gender CHAR(1) DEFAULT(‘F’),Salary NUMBER(5) NOT NULL,Dept NUMBER,constraint Emp_UQ UNIQUE(Fname, Lname)

);

Unique Constraint

The name of the constraint

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Primary Key Constraint

CREATE TABLE Employee(SSN NUMBER PRIMARY KEY,Fname VARCHAR2(20),Lname VARCHAR2(20),Gender CHAR(1) DEFAULT(‘F’),Salary NUMBER(5) NOT NULL,Dept NUMBER,constraint Emp_UQ UNIQUE(Fname, Lname)

);

Primary Key implies NOT NULL and UNIQUE. There can only be one primary key.

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Another Table

CREATE TABLE Department(DeptNum NUMBER PRIMARY KEY,Name VARCHAR2(20),ManagerId NUMBER

);

Shouldn’t all department numbers in Employee appear in Department?

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Foreign Key Constraint(Referential Integrity)

CREATE TABLE Employee(SSN NUMBER PRIMARY KEY,Fname VARCHAR2(20),Lname VARCHAR2(20),Gender CHAR(1) DEFAULT(‘F’),Salary NUMBER(5) NOT NULL,Dept NUMBER, constraint Emp_UQ UNIQUE(Fname, Lname),FOREIGN KEY (Dept) REFERENCES

Department(DeptNum));

Must be unique

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Alternative Notation

CREATE TABLE Employee(SSN NUMBER PRIMARY KEY,Fname VARCHAR2(20),Lname VARCHAR2(20),Gender CHAR(1) DEFAULT(‘F’),Salary NUMBER(5) NOT NULL,Dept NUMBER REFERENCES Department(DeptNum),constraint Emp_UQ UNIQUE(Fname, Lname)

);

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Understanding Foreign Keys

The constraint on the last table should be read as: “The field Dept in Employee is a foreign key that references the field DeptNum in Department”

Meaning: Every non-null value in the field Dept in Employee must appear in the field DeptNum in Department.

What happens to Employees in department 312 when Department 312 is removed from the Department table?

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Deleting a Referenced Value If nothing additional is specified, then Oracle will not allow Department 312 to be

deleted if there are Employees working in this department. If the constraint is written as

FOREIGN KEY (Dept) REFERENCES

Department(DeptNum) ON DELETE CASCADE

then Employees working in 312 will be deleted

automatically from the Employee table

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Cyclic Foreign Keys

CREATE TABLE Department(

DeptNum NUMBER PRIMARY KEY,

Name VARCHAR2(20),

ManagerId NUMBER REFERENCES Employee(SSN)

);

Do you see a problem in inserting data now?

We should revise the Department table:

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Solution to Cyclic Constraints

Add one of the constraints later on (after insertion):

ALTER TABLE Department

ADD(FOREIGN KEY (ManagerId)

REFERENCES Employee(SSN));

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Check Conditions

A check condition is a Boolean expression: “And”s and “Or”s of conditions of the type X > 5…

On a column: it can refer only to the column

On a table: it can refer only to multiple columns in the table

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Check Constraints

CREATE TABLE Employee(SSN NUMBER PRIMARY KEY,Fname VARCHAR2(20),Lname VARCHAR2(20),Gender CHAR(1) DEFAULT(‘F’)

CHECK(Gender = ‘F’ or Gender = ‘M’) ,

Salary NUMBER(5) NOT NULL,CHECK (Gender = ‘M’ or Salary > 10000)

);

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Table Alteration

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Altering Tables

Table definition can be altered after its creation Adding columns Changing columns’ definition Dropping columns Adding constraints And more…

Use the reserved word ALTER

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Altering Tables (continues)

Adding a column:ALTER TABLE Employee ADD (

Mname VARCHAR2(20),Birthday DATE

); Changing columns’ definition:

ALTER TABLE Emplyee Modify (Mname VARCHAR2(10)

);

Cannot be NOT NULL unless the

table is empty

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Altering Tables (continues)

Dropping columns:ALTER TABLE Employee DROP COLUMN

Mname;

Dropping multiple columns:

ALTER TABLE Employee DROP (Mname, Birthday);

Adding constraints:ALTER TABLE Department ADD(

FOREIGN KEY (ManagerId) REFERENCES Employee(SSN));

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Deleting a Table

To delete the table Employee :

DROP TABLE Employee;

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User’s Table List

ORACLE may print tables that hold some general information about the tables in your database

Such Tables are: Tab, Cat, User_Tables (too detailed...)

To see the list of all your tables you can print: SELECT * FROM Cat; SELECT tname FROM Tab; SELECT table_name from User_Tables;

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Table Data Maintenance

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The Employee Table

> Describe Employee

Name Null? Type-------- -------- ------------SSN NUMBERFNAME VARCHAR2(20)LNAME VARCHAR2(20)GENDER CHAR(1)SALARY NOT NULL NUMBER(5)

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Inserting a Row

To insert a row into the Employee table:INSERT INTO

Employee(SSN, Fname, Lname, Salary)

VALUES(121, ‘Sara’, ‘Cohen’,10000);

The remaining columns get default values (or NULL)

Order is not important

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Some More Details…

The fields needn’t be specified if values are specified for all columns and in the order defined by the table

Example:INSERT INTO Employee

VALUES(121, ‘Sara’, ‘Cohen’, `F’, 10000);

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Deleting Rows

General format:DELETE FROM Table WHERE Cond;

Deletes all rows satisfying Cond from Table For example, to remove the employee with

SSN 121 from the Employee table:DELETE FROM Employee WHERE

SSN = 121;

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Deleting Rows (continues)

To remove all male employees having a salary greater than 15000 shekels:

DELETE FROM Employee WHERE

Gender = ‘M’ AND Salary > 15000;

We will later discuss WHERE clauses…

Case sensitive

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Updating Rows (continues)

We can update fields of rows in a table General format:

UPDATE Table SET Field1=value1,,,FieldN=valueNWHERE Cond

Now we can reduce salaries instead of firing employees:

UPDATE Employee SET Salary = 15000 WHERE Gender = ‘M’ AND

Salary > 15000;

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The ORACLE Bulk Loader

A tool that provides easy insertion of large amounts of rows into tables.

The idea: the field values of the rows are kept in a file, the format of which is defined by us.

For example, it can automatically load 3 employees from the file myEmployees.dat that contains the following lines:

Sara|Cohen|121Benny|Kimelfeld|134Yaron|Kanza|156

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The Control File

The control file is the direct input of the loader A simple control file:

LOAD DATA

INFILE <dataFile> [APPEND] INTO TABLE <tableName> FIELDS TERMINATED BY '<separator>‘(<list of all attribute names to load>)

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The Control File (continues)

<dataFile>: The name of the data file

<tableName>: The name of the table into which the data will be loaded

(appended if APPEND is specified, or else the table must be empty)

<separator>: A string that separates two field values of a row

The attributes are separated by commas and enclosed in parentheses

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The Control File (continues)

As an example, the following control file loads the employees from myEmployees.dat:

LOAD DATA

INFILE myEmployees.dat INTO TABLE Employees FIELDS TERMINATED BY '|' (Fname, Lname, SSN)

The attributes that are unspecified will be set to NULL

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The Data File

The Bulk Loader considers every single line to represent one row in the table Even an empty line! (which will usually result in

an error) Spaces are not ignored in the data file!

thus the rows ‘sara| cohen|121’ and ‘sara|cohen|121’ define different functionalities

The NULL value is implied by the NULL keyword or the empty string

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The Data File (continues)

The control and the data files can be combined into one .ctl file using the following format:

LOAD DATA INFILE *INTO TABLE Employees FIELDS TERMINATED BY '|' (Fname, Lname, SSN)BEGINDATA Sara|Cohen|121Benny|Kimelfeld|134Yaron|Kanza|156

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The Bulk Invocation

To invoke the bulk loader, issue the following command directly from the Unix shell:sqlldr <yourName> control=<ctlFile> log=<logFile> bad=<badFile>

All fields are optional File names that have no extension are

automatically extended (by .dat, .log or .bad) Erroneous lines in the data file are ignored

and written into badFile, and any other relevant information is written into logFile.

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Bulk Loader Important Remarks

Before using the Bulk Loader, make sure your personal ORACLE environment is properly set up

The tables you fill using the Bulk Loader should be created prior to the loader invocation

Before invoking the Bulk Loader you have to make sure that NO SQLPLUS SESSIONS ARE OPENNED!

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Table Printing and Formatting

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Format Example

Consider the following table print:

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Format Example (continues)

Absolutely not readable! Solution: we write some commands in a format file

and we get:

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Printing a Table

To print a table use the sql command: SELECT * FROM table_name;

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Add a Title

We can add a title to a table printing page using the command: TTITLE ‘title’

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Change a Column’s Heading

We can change a column’s heading using the command: COLUMN ‘col_name’ HEADING ‘heading’

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Define a Column Size

We can define the size of a column: COLUMN ‘col_name’ format ‘format’ Format Examples:

a18: an ASCII text of size 18 90.99: a number with 4 digits, a decimal point,

minus sign (for negative numbers) and 0 before the dot for numbers smaller than 1

We can ask ORACLE to cut words to fit the defined space using the command: COLUMN ‘col_name’ truncated

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Define a Column Size

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The Whole Picture