ITBIS373 Database Development Lecture 3a - Chapter 3: Using SQL Queries to Insert, Update, Delete, and View Data

ITBIS373 Database Development

Lecture 3a - Chapter 3: Using SQL Queries to Insert, Update, Delete, and View Data

Guide to Oracle 10g 2

Lesson A Objectives

After completing this lesson, you should be able to: Run a script to create database tables automatically Insert data into database tables Create database transactions and commit data to the

database Create search conditions in SQL queries Update and delete database records and truncate

tables


Lesson A Objectives (continued)

Create and use sequences to generate surrogate key values automatically

Grant and revoke database object privileges


Using Scripts to Create Database Tables

Script Text file that contains one or more SQL

commands Run a script

Type start at SQL prompt Blank space Full path and filename of script file


Running a script:SQL> START path_to_script_file; Path cannot contain any blank spaces

SQL Scripts


Using SQL*PLUS to Insert Data After successfully running the script to create the tables, you

already to begin adding data to them. In business setting, programs called forms are used to automate the data entry process. Program developers who create forms often use the SQL INSERT statement in the form program code to insert data into tables.


Using the INSERT Command

Basic syntax for inserting into every column:INSERT into tablename

VALUES (column1_value, column2_value, … );

Basic syntax for inserting into selected columnsINSERT into tablename (columnname1, columnname2, … );

VALUES (column1_value, column2_value, … );

CE

There is no slide for A-head "Inserting Data into Tables" (pg 88) - okay?


Using the INSERT Command (continued)

Ensure all foreign keys that new row references have already been added to database




Inserting Selected Table Fields


Format Models

Also called format mask Used to specify different output format from

default For NUMBER data types

9 represents digit For DATE/TIMESTAMP data types

Choose formats for year day, date, etc.


Inserting Date and Interval Values

Inserting values into DATE columns Use TO_DATE function to convert string to DATE Syntax

TO_DATE('date_string', 'date_format_model')

Inserting values into INTERVAL columns Syntax

TO_YMINTERVAL('years-months') TO_DSINTERVAL('days HH:MI:SS.99')


Inserting Date Values





Creating Transactions and Committing New Data

When you create a new table or update the structure of an existing table, the DBMS changes the rows immediately and makes the change visible to other users. This is not the case when you insert, update, or delete data rows. The commands for operations that add, update, or delete data are called action queries.

All three action queries need to succeed, or non of them should succeed.

After the user enters all of the action queries in a transaction, he or she can either COMMIT (save) all of the changes or ROLL BACK (discard) all of the changes


The purpose of transaction processing is enable every user to see a consistent view of the database. To achieve this consistency, a user cannot view or update data values that are part of another user’s uncommitted transaction because these uncommitted transactions, which are called pending transactions, might be rolled back.

The Oracle DBMS implements transaction processing by locking data rows associated with pending transactions. When the DBMS locks a row, other users cannot view or modify the row. When the user commits the transaction, the DBMS releases the lock on the rows, and other users can view and update the rows again.


A transaction starts when you type one or more DML commands in SQL*Plus

A transaction ends when you issue either the COMMIT or ROLLBACK command SQL>COMMIT;

SQL>ROLLBACK;

Transactions


Committing and Rolling Back Data

COMMIT Makes transaction command changes permanent

in the database and visible to other users ROLLBACK

Rolls back transaction command changes and restores database to its state before the transaction



Used to mark individual sections of a transaction

You can roll back a transaction to a savepoint

Savepoint


Syntax:UPDATE tablename

SET column1 = new_value,

column2 = new_value, …

WHERE search_condition; Records can be updated in only one

table at a time Can update multiple records if they all

match the search condition

Updating Records



The general syntax of a SQL search condition is:

WHERE columnname comparison_operator search_expression

Search Conditions



Defining Search Expressions

NUMBER example WHERE f_id = 1

Character data example WHERE s_class = 'SR'

DATE example WHERE s_dob = TO_DATE('01/01/1980', ‘MM/DD/YYYY')



Creating Complex Search Conditions

A complex search condition combines multiple search conditions using the AND,OR, and NOT logical operators.

EX The following complex search condition matches all rows in which

BLDG_CODE is ‘CR’ and the capacity is greater than 50: WHERE bldg_code =‘CR’ AND capacity >50 The following search condition matches all course section rows that

meet either on Tuesday and Thursday or on Monday, Wednesday, and Friday (at Northwoods University):

WHERE day=‘MW’ OR day =‘UTH’


Deleting Table Rows You use the SQL DELETE action to remove specific

rows from a database table, and you truncate the table to remove all of the table rows.

The SQL DELETE Action QueryThe general syntax for DELETE action query is: DELETE FROM tablename WHERE search condition;EX In the following set of steps, you delete Tammy Jones from the STUDENT

table. You specify ‘Tammy’ and ‘Jones’ in the action query’s search condition.



Deletes multiple records if search condition specifies multiple records

If search condition is omitted, all table records are deleted

You can’t delete a record if it contains a primary key value that is referenced as a foreign key

Deleting Records


Truncating Tables

When you need to delete all of the rows in a table quickly, you can truncate the table, which means you remove all of the table data without saving any rollback information.

TRUNCATE TABLE tablename;

You cannot truncate a table that has foreign key constraints enabled.


Ex:Ex: You truncate the LOCATION table to delete all of its rows. Recall that the LOC_ID column in the LOCATION table is a foreign key in both the FACULTY table and the COURSE_SECTION table, so you must first disable the LOC_ID foreign key constraints in the FACULTY and COOURSE_SECTION tables. Then you truncate the LOCATION table.



Sequential list of numbers that is automatically generated by the database

Used to generate values for primary key identifier

Has no real relationship to row to which it is assigned other than to identify it uniquely

Surrogate key values automatically generated using a sequence.

Sequences



Creating New Sequences

CREATE SEQUENCE command DDL command No need to issue COMMIT command

CE

There is no slide for A-head "Sequences" (pg 105) - okay?


General Syntax Used to Create a New Sequence

CE

This slide's title is figure caption rather than A-head (like slide 23) - okay?



Viewing Sequence Information

Query the SEQUENCE Data Dictionary View:


Using Sequences

CURRVAL Returns most recent sequence value retrieved

during the current user session. NEXTVAL

Next available sequence value sequence_name.NEXTVAL



Using Sequences (continued)

DUAL Simple table in system user schema More efficient to retrieve pseudocolumns from

DUALSELECT sequence_name.NEXTVAL

FROM DUAL;

DBMS uses user sessions To ensure that all sequence users receive unique

sequence numbers


Pseudocolumns

Acts like a column in a database query Actually a command that returns a specific

values Used to retrieve:

Current system date Name of the current database user Next value in a sequence


Pseudocolumn Examples

Pseudocolumn

Name

Output

CURRVAL Most recently retrieved sequence value

NEXTVAL Next value in a sequence

SYSDATE Current system date from database server

USER Username of current user


- Retrieving the current system date:SELECT SYSDATE

FROM DUAL;

- Retrieving the name of the current user:SELECT USER

FROM DUAL;

- DUAL is a system table that is used with pseudocolumns

Using Pseudocolumns


EX To create the ITEMID_SEQUENCE SQL> CREATE SEQUENCE itemid_sequence START WITH 996 NOMAXVALUE NOCACHE; sequence created To access the next value in a sequence and use that value when

you insert a new data record, use the following general command: INSERT INTO <table name> VALUES(<owner user name>_<sequence name>.NEXTVAL,<field2

data value>,<field3 data value>,… This command assumes that the primary key associated with

the sequence is the first table field.


SQL> INSERT INTO item VALUES(itemid_sequence.NEXTVAL, ’Heavey duty day pack’, ‘outdoor gear’); SQL> Select itemid, itemdesc From item; ITEMID ITEMDESC 894 ------- 897 ------- 559 ------- 786 ------ 996 Heavy duty day pack


SQL > Insert into item values(item_sequence.nextval,’mountain parka’,’clothing’) ITEMID ITEMDESC 894 ------- 897 ------- 559 ------- 786 ------ 996 Heavy duty day pack 997 Mountain parka

SQL> select itemid_sequence.nextval from dual; Nextval 998


Deleting Sequences

To delete a sequence from the database, you use the DROP SEQUENCE DDL command.

Ex: to drop LOC_ID_SEQUENCE, you use the command

DROP SEQUENCE loc_id_sequence;


Permissions that you can grant to other users to allow them to access or modify your database objects

Granting object privileges:GRANT privilege1, privilege2, …ON object_nameTO user1, user 2, …;

Revoking object privileges:REVOKE privilege1, privilege2, …ON object_nameFROM user1, user 2, …;

Object Privileges


Examples of Object Privileges

Privilege Description

ALTER Allows user to change object’s structure using the ALTER command

DROP Allows user to drop object

SELECT Allows user to view object

INSERT, UPDATE, DELETE

Allows user to insert, update, delete table data

ALL Allows user to perform any operation on object




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ITBIS373 Database Development Lecture 3a - Chapter 3: Using SQL Queries to Insert, Update, Delete, and View Data