Using SQL queries to insert update, delete, and view data

A Guide to Oracle9i 2Lesson A Objectives • Learn how to run a script to create database tables automatically • Learn how to insert data into database tables • Learn how to create databas

A Guide to Oracle9i 1

Using SQL Queries to Insert,

Update, Delete, and View Data

Chapter 3

A Guide to Oracle9i 2

Lesson A Objectives

• Learn how to run a script to create database tables

automatically

• Learn how to insert data into database tables

• Learn how to create database transactions and commit data

to the database

• Create search conditions in SQL queries

• Understand how to update and delete database records,

and how to truncate tables

• Learn how to create and use sequences to generate

surrogate key values automatically

• Learn how to grant and revoke database object privileges

• Usually have sql extension

• To run from SQL*Plus:

– Start full file path (c:\temp\myfile.sql)

– @full file path (@c:\temp\myfile.sql)

– Extension can be omitted if it is sql

A Guide to Oracle9i 4

Inserting Data into Tables

• INSERT command adds new records

• Field values should match column order, or be

specified in command

• INSERT INTO faculty (F_ID, F_LAST, F_FIRST,

F_MI, LOC_ID) VALUES (1, 'Cox', 'Kim', 'J', 9);

A Guide to Oracle9i 5

Format Models

• Used to format data retrieved from database

• Can be used to format a date to display time

or a number to display as a currency

A Guide to Oracle9i 6

Numerical Format Models

A Guide to Oracle9i 7

Date Format Models

A Guide to Oracle9i 8

Date Format Models

A Guide to Oracle9i 9

Inserting Date and Interval Values

• Use to_date function to convert a character string to a date

– Specify date string and matching format model

– TO_DATE('08/24/2004', 'MM/DD/YYYY')

– TO_DATE('10:00 AM', 'HH:MI AM')

• Use functions to convert character strings to intervals

– TO_YMINTERVAL('4-9') inserts a positive interval of 4 years, 9

months

– TO_DSINTERVAL('0 01:15:00') inserts a positive interval of 4 days,

1 hour, 15 minutes, 0 seconds

A Guide to Oracle9i 10

Inserting LOBs

• Before inserting LOB must insert a LOB locator

• LOB locator: a structure that contains information

that identifies the LOB data type and points to the

alternate memory location

• Write a program or use a utility to add LOB data to database

• Use EMPTY_BLOB() function to insert a LOB locator

A Guide to Oracle9i 11

Creating Transactions and

Committing New Data

• Transaction: series of action queries that represent a logical unit of

work

• User can commit (save) changes

• User can roll back (discard) changes

• Pending transaction: a transaction waiting to be committed or

rolled back

• Oracle DBMS locks records associated with pending transactions

• Other users cannot view or modify locked records

A Guide to Oracle9i 12

Commit and Roll Back in SQL*Plus

• Transactions begin automatically with first command

• Type COMMIT to commit changes

• Type ROLLBACK to roll back changes

• Used in SELECT, UPDATE and DELETE statements

• WHERE fieldname comparison_operator

search_expression

• WHERE S_ID = 1

A Guide to Oracle9i 15

Comparison Operators

A Guide to Oracle9i 17

Creating Complex Search Conditions

• Combines multiple search conditions using the

AND,OR, and NOT logical operators.

• AND – both conditions must be true

• OR – one or both condition must be true

• NOT – opposite of actual value

• Use () to group logical operators

A Guide to Oracle9i 18

Updating and Deleting Existing Table Records

• UPDATE:

– Updates field values in one or more records in a table

– Only one table may be updated at a time

– UPDATE tablename SET field1= new_value1, field2 = new_value2,

WHERE search condition;

• DELETE:

– Removes specific records from a database table

– If search condition is omitted, entire table data is removed

– DELETE FROM tablename WHERE search condition;

– SELECT sequence_name.NEXTVAL FROM DUAL;

– INSERT INTO location LOC_ID)

VALUES(loc_id_sequence.NEXTVAL);

A Guide to Oracle9i 21

Database Object Privileges

• Privileges must be granted so that other users can access objects in user schema

• GRANT privilege1, privilege2,…ON object_name TO user1,user2, ;

• REVOKE privilege1, privilege2, ON object_name FROM user1,

user2, ;

• To grant or revoke privileges for everyone use PUBLIC as user

A Guide to Oracle9i 22

Lesson B Objectives

• Learn how to write SQL queries to retrieve data from

a single database table

• Create SQL queries that perform calculations on

retrieved data

• Use SQL group functions to summarize retrieved

data

A Guide to Oracle9i 23

Retrieving Data from

a Single Database Table

• SELECT fieldname1, fieldname2, FROM

ownername.tablename WHERE search_condition;

• To select:

– All rows omit where clause

– All fields, use *: SELECT * FROM …

– Only unique field values: SELECT DISTINCT fieldname

• Search condition:

– Use comparison and logical operators

– IS NULL/IS NOT NULL to match/exclude NULL values

– IN/NOT IN to match set values

– LIKE with wildcards % and _ to match character strings

A Guide to Oracle9i 24

Sorting Query Output

• Use ORDER BY sort_key_field(s)

• Default order is ascending, use DESC to sort descending

A Guide to Oracle9i 25

Using Calculations in SQL Queries

• Calculations are performed by DBMS, result only sent to client

• Can use arithmetic operators (+, -, *, /)

• Place calculation in select clause: SELECT price * quantity

FROM …

• Calculations can be performed on NUMBER, DATE and

INTERVAL fields only

• Single-row functions: built in Oracle functions to perform

calculations and manipulate retrieved data values

A Guide to Oracle9i 26

Oracle9i SQL Group Functions

• Group functions: perform an operation on a group of queried

rows and returns a single result

A Guide to Oracle9i 27

Group By

• Use to group output by the field with duplicate values and apply group functions to the grouped data

A Guide to Oracle9i 28

Having

• Use to place a search condition on results of group function

calculations

• Like “WHERE” for group functions

• HAVING group_function comparison_operator value

• HAVING SUM(capacity) >= 100

A Guide to Oracle9i 29

Formatting Output in SQL*Plus

• To change default column headings:

– Specify alternate column headings: SELECT fieldname1

"heading1_text", fieldname2 "heading2_text",

– Use an alias for column headings: SELECT fieldname1 AS

alias_name1

• To change SQL*Plus line and page size settings

– Select Options/Environment on menu bar

– Modify linesize and pagesize to desired values

A Guide to Oracle9i 30

Formatting Numbers and Dates

• Use to_char function with format models

• TO_CHAR(field_name, 'format_model')

• SELECT inv_id, TO_CHAR(inv_price, '$99,999.99')

FROM inventory WHERE item_id = 1;

A Guide to Oracle9i 31

Lesson C Objectives

• Learn how to create SQL queries that join multiple tables

• Learn how to create nested SQL queries

• Understand how to combine query results using set operators

• Create and use database views

A Guide to Oracle9i 32

Joining Multiple Tables

• Join: combine data from multiple database tables using foreign key references

• SELECT field1, field2, FROM table1, table2 WHERE

table1.joinfield = table2.joinfield AND search_condition(s);

• If tables share field names, must prefix field in select with table name (table1.field1, table2.field1)

• Join condition: part of where clause indicating how tables are related (table1.foreign_key = table2.primary key)

• Search conditions can be added to join condition using AND operator

A Guide to Oracle9i 33

Inner Join

• Join two tables based on values in one table being equal

to values in another table

• Also known as equality join, equijoin or natural join

• Returns results only if records exist in both tables

A Guide to Oracle9i 34

Joining Via Linking Table

A Guide to Oracle9i 35

Using a Query Design Diagram

• Helpful for creating complicated queries

• Can use a formula to derive actual query from diagram

A Guide to Oracle9i 36

Outer Join

• Returns all rows in one table and matching rows in joined table

• Inner table: all rows are returned

• Outer table: matching rows are returned

• Outer table marked with a + in join condition

• inner_table.join_field = outer_table.join_field(+)

• Null values are inserted for fields in outer table that are not

found

A Guide to Oracle9i 37

Self-Join

• A query that joins a table to itself

• Used when a table has a foreign key relationship to itself

(usually parent-child relationship)

• Must create a table alias and structure the query as if you are joining the table to a copy of itself

• FROM table1 alias1,

• Use alias, not table name for select and where clauses

A Guide to Oracle9i 38

Self-Join Example

A Guide to Oracle9i 39

Creating Nested Queries

• Used to select results based on the result of a query

• Consists of a main query and one or more subqueries

– Main query: first query that appears in the SELECT command

– Subquery retrieves values that the main query’s search condition

must match

A Guide to Oracle9i 40

Creating Nested Queries

• Nested queries can return single or multiple values

– To match single values use = operator

– To match multiple values use IN operator

• Subqueries can be nested to more than one level (nested

subqueries)

• Nested subqueries are slower than joins and should be used sparingly

A Guide to Oracle9i 41

Nested Subquery Example

A Guide to Oracle9i 42

Using Set Operators

To Combine Query Results

• Use to select data from multiple tables not connected with

foreign key relationships

• UNION suppresses duplicate values

• UNION ALL includes duplicate values

• INTERSECT takes only matching fields

• MINUS takes only fields in query1 not query2

A Guide to Oracle9i 44

Creating and Using Database Views

• Similar to storing the result of a query in the database

• Based on a source query that:

– can specify a subset of a single table’s fields or records

– can join multiple tables

• Can be used to enforce security (user has access to view but not underlying table)

A Guide to Oracle9i 45

Creating and Using Database Views

• Views can be updateable if:

– SELECT clause contains only fieldnames, no functions or

calculations

– cannot contain the ORDER BY, DISTINCT, or GROUP BY clauses, group functions, or set operators

– search condition cannot contain a nested query

• Views are used like tables for selecting, inserting, updating and deleting data (only updatable views can be modified)

A Guide to Oracle9i 46

Creating and Deleting Views

• CREATE OR REPLACE VIEW view_name AS source_query;

• DROP VIEW viewname;

A Guide to Oracle9i 47

Summary

• Use INSERT commands to add data

• NUMBER, DATE and INTERVAL data types can be converted

to and from character strings using format models

• Database changes are made within a transaction that can be committed or rolled back

• Use search conditions to specify records to update, delete or select

• Arithmetic, logical, grouping, and built-in Oracle functions can

be used to specify search conditions and manipulate data

• Query output can be formatted by modifying SELECT clause

• Queries can be “saved” by creating a view

• Views can be used like tables to select, insert, update and

delete data