Enhanced Guide to Oracle 10g
Chapter 3:
Using SQL Queries to Insert,
Update, Delete, and View Data
Guide to Oracle 10g
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Queries and action queries
 Queries are the DML commands that allow users
to retrieve database data, because the retrieved
data are answers to questions.
 Action queries are the DML commands that insert,
update, or delete database data, because the
commands perform an action that change the data
value.
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SQL Scripts
 Script: text file that contains a sequence of SQL
commands.
 Usually have .sql extension
 Running a script:
SQL> START path_to_script_file;
OR
SQL> @ path_to_script_file;

Path cannot contain any blank spaces
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Inserting a Value Into Every
Field in a Record
 Syntax:
INSERT INTO tablename VALUES
(column1_value, column2_value, …);
 You must insert a value or a NULL placeholder
for every field.
 Fields must be entered in the order they appear
in the table when you issue the DESCRIBE
command.
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Inserting a Value Into Every
Field in a Record

Example:
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Inserting Selected Table Fields
 Command to insert values for selected
record fields:
INSERT INTO tablename
(column1_name, column2_name, …)
VALUES
(column1_value, column2_value, …);
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Inserting Selected Table Fields
 Example:
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Format Models (Masks)


All data is stored in the database in a
standard binary format
Format masks are alphanumeric text
strings that specify the format of input
and output data


Table 3-1: Number format masks
Table 3-2: Date format masks
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Inserting Date Values
 Date values must be converted from
characters to dates using the TO_DATE
function and a format mask
 Example:
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Inserting Text Data
 Must be enclosed in single quotes
 Is case-sensitive
 To insert a string with a single quote,
type the single quote twice
 Example:
'Mike''s Motorcycle Shop'
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Inserting Interval Values
 Year To Month Interval:
TO_YMINTERVAL(‘years-months’)
e.g. TO_YMINTERVAL(‘3-2’)
 Day To Second Interval:
TO_DSINTERVAL(‘days HH:MI:SS.99’)
e.g. TO_DSINTERVAL(‘-0 01:15:00’)
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Inserting LOB Column Locators
 Oracle stores LOB data in a separate physical
location from other types of data in a row.
 Before inserting data in a LOB column, a locator
must be inserted first.
 A locator is a structure that contains information that
identifies the LOB data type and points to the
alternate memory location.
 After that a program or a utility is needed to insert
the data into the DB (chapter 10).
 Ex. To create a locator for a BLOB data:
 EMPTY_BLOB();
 Another example page 96.
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Transactions
 Transaction
 Logical unit of work consisting of one or
more SQL DML commands
 INSERT, UPDATE, DELETE
 All transaction commands must succeed or
none can succeed
 Transaction results are not visible to
other users until they are “committed”
to the database (this is not the case with DDL commands)
 Until a transaction is committed, it can
easily be “rolled back” (undone)
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Transactions
 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;
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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
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Savepoints
 Used to mark
individual
sections of a
transaction
 You can roll
back a
transaction to
a savepoint
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Search Conditions
 Format:
WHERE fieldname operator expression
 Operators









Equal (=)
Greater than, Less than (>, <)
Greater than or Equal to (>=)
Less than or Equal to (<=)
Not equal (< >, !=, ^=)
LIKE
BETWEEN
IN
NOT IN
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Search Condition Examples
WHERE s_name = ‘Sarah’
WHERE s_age > 18
WHERE s_class <> ‘SR’
 Text in single quotes is case sensitive
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Updating Records
 Syntax:
UPDATE tablename
SET column1 = new_value,
column2 = new_value, …
WHERE search_condition;
 Each update statement can update
row(s) in one table only
 Can update multiple records if they all
match the search condition
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Deleting Records
 Syntax:
DELETE FROM tablename
WHERE 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
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Truncating Tables

Removes ALL table data WITHOUT
saving any rollback information (DELETE needs to
save a copy of all the deleted records for a rollback possibility)



Advantage: fast way to delete table data
Disadvantage: can’t be undone (rollback)
Syntax:
TRUNCATE TABLE tablename;
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Truncating Tables


You can not truncate a table that has an
enabled foreign key constrain. So you
need to disable the constraint first:
Syntax:
TRUNCATE TABLE tablename
DISABLE CONSTRAINT constraint_name;
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Sequences
 Sequential list of numbers that is
automatically generated by the
database
 Used to generate unique values
for surrogate keys
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Creating Sequences
 Syntax:
CREATE SEQUENCE sequence_name
[optional parameters];
 Example:
CREATE SEQUENCE f_id_sequence
START WITH 200;
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Viewing Sequence Information

Query the SEQUENCE Data Dictionary
View: (user_sequences) see table 2.3 p.69
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Pseudocolumns



To use sequences, psedocolumns should be
understood first.
Psedocolumns acts like a column in a
database table, but it is actually a
command that returns a specific value.
Used to retrieve:



Current system date
Name of the current database user
Next or Current values of a sequence
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Pseudocolumn Examples
Pseudocolumn Output
Name
CURRVAL
Most recently retrieved
sequence value
NEXTVAL
Next value in a sequence
SYSDATE
Current system date from
database server
USER
Username of current user
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Using Pseudocolumns
 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. It contains one column. Its
value can not be deleted or modified. (P.110)
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Using Pseudocolumns
With Sequences
 Accessing the next value in a sequence:
sequence_name.NEXTVAL

(Can you know the retrieved value before using it?) see next slide.
 Inserting a new record using a
sequence:
INSERT INTO my_faculty VALUES
(f_id_sequence.nextval, ‘Professor Jones’);
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Seeing value of sequences
 The following command shows the NEXT value of the
sequence:
 SELECT sequence_name.NEXTVAL FROM DUAL;
 The following command shows the current value of the
sequence:
 SELECT sequence_name.CURRVAL FROM DUAL;
 See example page 111.
 Accessing CURRVAL without NEXTVAL in advance cause an error.
See example page 112.
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Deleting Sequencing
 The following DDL command drops sequences from a DB:
 DROP SEQUENCE sequence_name;
 No need for commit with DDL commands.
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Object Privileges

Permissions that you can grant to other users to allow them to access
or modify your database objects
Object Type
Privilege
Description
Table,
Sequence
ALTER
Allows user to change object’s structure
using the ALTER command
Table,
Sequence
DROP
Allows user to drop object
Table,
Sequence
SELECT
Allows user to view object
Table
INSERT,
UPDATE,
DELETE
Allows user to insert, update, delete table
data
Any database
object
ALL
Allows user to perform any operation on
object
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Syntax
Granting object privileges:

GRANT privilege1, privilege2, …
ON object_name
TO user1, user 2, …;
Revoking (cancel) object privileges:

REVOKE privilege1, privilege2, …
ON object_name
FROM user1, user 2, …;
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Granting and Revoking Object
Privileges
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Retrieving Data From
a Single Table
 Syntax:
SELECT column1, column2, …
FROM tablename
WHERE search_condition;
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Retrieving Data From
a Single Table
 To retrieve every column in a table:
SELECT * FROM …
 To retrieve every record in a table,
omit the search condition
SELECT column1, column2, …
FROM tablename;
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Qualifying Table Names

If you retrieve data from a table that is owned by
another user, you must qualify the table name by
prefacing it with the owner’s name. (we will study it again when
joining multiple tables P.159)
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Suppressing Duplicate Records
 Sometimes queries retrieve
duplicate records
 To suppress duplicate
outputs, use the DISTINCT
qualifier:
SELECT DISTINCT
column1, column2, …
FROM ...
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Using Multiple Search
Conditions
 Use the search condition (where) to retrieve rows
matching specific criteria.
 Combining search conditions
 AND: both conditions must be true
 OR: either condition can be true
 Combining AND and OR in a single operation
 AND comparisons are evaluated first
 Always use parentheses to force conditions to be
evaluated in the correct order
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Example
SQL> SELECT room
2. FROM location
3. WHERE bldg_code = ‘BUS’
4. AND capacity >= 40;
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Searching for NULL Records
 NULL: not defined
 Use IS NULL search condition
SELECT s_name, s_class
FROM my_students
WHERE s_class IS NULL;
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Searching for
NOT NULL Records
 Use IS NOT NULL operator
SELECT s_name, s_age
FROM my_students
WHERE s_class IS NOT NULL;
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Using the IN and NOT IN
Operators

IN retrieves all values where the search
column value matches a set of values
SELECT *
FROM enrollment
WHERE grade IN (‘A’, ‘B’);
Either A or B.
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Using the IN and NOT IN
Operators

NOT IN retrieves all values where the search
column value matches a set of values
SELECT *
FROM enrollment
WHERE grade NOT IN (‘A’, ‘B’);
Neither A or B.
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Using the LIKE Operator

Performs inexact searches by matching
part of a character string
WHERE fieldname LIKE character_string;
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Using the LIKE Operator

Character string must be in single quotes and use
wildcard characters

(%) represents multiple wildcard characters



(_) Underscore represents a single wildcard character


‘%2006’ Exact search of a string its right characters same as
‘2006’, it ignores anything on the left (no matter how many
characters are there).
‘FALL%’ all rows in which the first 4 characters are FALL.
‘_R’ retrieve all values its first character can be any value, but
the second must be ‘R’.
Wildcard characters can be placed at beginning or end
of string
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Examples Using the LIKE Operator

SELECT * from term
WHERE term_desc LIKE ‘Fall%’;

SELECT course_no FROM course
WHERE course_no LIKE ‘%1__’;
Two
underscores
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Sorting Query Output
 Use the ORDER BY clause
 Specify sort key, which is the
column used as a basis for ordering
the output data
SELECT s_name, s_age
FROM my_students
ORDER BY s_age;
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Sorting Query Data
 Default sort order
 Numerical: ascending
 Character: A - Z
 Date: oldest - newest
 To force the sort order: use ASC or DESC
 Example
SELECT s_name, s_age
FROM my_students
ORDER BY s_age DESC;

You can specify multiple sort keys.
Example P. 131.
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Using Calculations in Queries
 Calculation using SQL directly is efficient, because
the result is returned to the client calculated.
 Arithmetic operations on retrieved data




Addition (+)
Subtraction (-)
Multiplication (*)
Division (/)
 Calculations are performed on NUMBER, DATE, and
INTERVAL data types.
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Example Calculations in Queries
 SELECT inv_id, inv_qoh * inv_price
FROM inventory;


Date calculations involve the current
date.
To retrieve the current date from the
server use:


SELECT SYSDATE FROM DUAL;
And then use it in equations:

SYSDATE – o_date
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Example Calculations in Queries
 Remember that time_enrolled is an
INTERVAL data type in STUDENT table.
 SELECT s_id, s_last, SYSDATE – time_enrolled
FROM student;
 Remember to use SELECT SYSDATE FROM
DUAL first.
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Single-Row
Number Functions
 Called so, because they return a single result for each row
of data retrieved.
 ABS - absolute value
 CEIL – rounds a number up to the next integer
 FLOOR – rounds a number down to the previous integer
 MOD – returns the remainder of a number and a divisor
 POWER - raises a number to an exponent
 ROUND - rounds a number
 SQRT – returns the square root of a value
 TRUNC - truncates a number to the nearest whole number
 Table 3-7 P. 137.
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Using Single-Row
Number Functions
 Example:
SELECT s_name,
TRUNC((SYSDATE - s_dob)/365)
FROM my_students;
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Single-Row
Character Functions
 CONCAT – joins 2 character strings
 INITCAP – returns a string with the initial letter only
uppercase
 LENGTH – returns the length of a string
 LPAD, RPAD – returns a string with a specific number of
characters added on the left or right side
 LTRIM, RTRIM – returns a string with all instances of a
specific character trimmed from the left or right side
 REPLACE – replaces all instances of a character with
another character
 UPPER/LOWER – returns a string in all upper/lower case
letters
 Table 3-8 P. 139
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Using Single-Row
Character Functions
 Example:
SELECT UPPER(s_name)
FROM my_students;
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Date Arithmetic
 To find a date that is a specific
number of days before or after a
known date, add or subtract the
number from the known date
 Example:
SELECT order_date + 30
FROM cust_order;
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Date Arithmetic
 To find the number of days
between two known dates,
subtract the later date from the
earlier date
 Example:
SELECT SYSDATE – s_dob
FROM my_students;
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Single-row Date Functions
 ADD_MONTHS
 returns a date that is a specific number of
months after a given date
 Example:
SELECT ADD_MONTHS(SYSDATE, 6)
FROM dual;
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Date Functions
 LAST_DATE
 Returns the date that is the last day
of the month specified in the current
date
 Example:
SELECT LAST_DATE(order_date)
FROM cust_order
WHERE order_id = 1057;
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Date Functions
 MONTHS_BETWEEN
 Returns the number of months between two
input dates
 Example:
SELECT MONTHS_BETWEEN(order_date, SYSDATE)
FROM cust_order
WHERE order_id = 1057;
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Group Functions
 Used to perform an operation on a
field from a group of retrieved records





AVG (average of all retrieved values)
COUNT (number of records retrieved)
MAX (maximum value retrieved)
MIN (minimum value retrieved)
SUM (sum of all retrieved values)
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Group Function Examples
SELECT
SELECT
SELECT
SELECT
AVG
MAX
MIN
SUM
(s_age)
(s_age)
(s_age)
(s_age)
FROM
FROM
FROM
FROM
Guide to Oracle 10g
my_students;
my_students;
my_students;
my_students;
63
Using the GROUP BY Clause
 Group the output by the column with duplicate values and apply
group functions to the grouped data.
 Example:
SELECT bldg_code, SUM(capacity)
FROM location
GROUP BY bldg_code;
 The bldg_code has 3 values(CR,BUS,LIB) see page 31.
Each value has several occurrences, BUS=7 times. So
the query group the occurrences of each value and
AVG the capacity of each. See result page 145.

Note that AVG(capacity)without group by gives
different results. NOT as desired. THINK!
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Using the HAVING Clause
 Is used to filter grouped data. It can be used to place
condition on the results of queries that display group
function calculation.
 Example:
SELECT bldg_code, SUM(capacity)
FROM location
HAVING SUM(capacity) >= 100
GROUP BY bldg_code;
 Here we are interested in the total
capacity of more than 99 for each building.
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Creating Alternate Column
Headings in SQL*Plus
Formatting output: did you notice the output of the queries? the column
name appeared as it is in the DB or the calculation formula.

To display a different headings:

Syntax:
SELECT column1 “heading1”, column2 “heading2”, …


Example:
SELECT bldg_code “Building”, SUM(capacity) “Building
Capacity”
FROM location
GROUP BY bldg_code;
Might contain spaces. Example (Building Capacity)
See output page 147.
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Creating a Column Alias


Column alias: is an alternate column name that can be
referenced in the ORDER BY and GROUP BY clauses
Syntax:
SELECT column1 AS alias1 …
 Example:
SELECT (SYSDATE – s_dob) AS age_alias
ORDER BY age_alias
Can NOT contain space.
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SQL* Plus Environment




Options  Environment
Linessize Custom  120 (char/line)
Pagesize  Custom  40 (line/page)
OK
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Formatting Data Using the
TO_CHAR Function
Used to display NUMBER and DATE values using a specific
format mask (model table 3-2 page 92)
 Syntax:
TO_CHAR(fieldname, ‘format_mask’);

Note the single quote.
Example
SELECT c_sec_id, sec_num,c_sec_day,
TO_CHAR(c_sec_time, ‘HH:M1 AM’)
FROM course_section;

See output page 152. See example page 152 for currency format.
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Join Queries


Retrieve data from multiple tables by joining tables using foreign key
references
Syntax
SELECT col1, col2, …
FROM table1, table2
WHERE table1.joincol = table2.joincol
AND search_condition(s);



Qualify a column by specifying the table that contains the column
followed by a period and then the column name.
The WHERE clause contains the join condition, which contains the
foreign key reference and the primary key in the other table.
Search condition is added using AND or OR operators.
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Join Queries Types

Join query types:




Inner (equality)
Outer
Self
Inequality
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Inner Joins

Occurs when joining two tables based on
values in one table being equal to values in
another table.
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Inner Joins
 Syntax:
SELECT column1, column2, …
FROM table1, table2
WHERE table1.join_column =
table2.join_column
Join condition
 You must include a join condition for every
link between 2 tables
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Inner Joins
 Example:
SELECT s_name, f_name
FROM student, faculty
WHERE student.f_id =
faculty.f_id;
 If you have N tables in the FROM
clause, you must have (N - 1) join
conditions
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Inner Joins
 If the tables have a single commonly named
and defined column, you can use the NATURAL
JOIN keywords to join the tables. See example figure 3
43 page 161.
Example
SELECT s_name, f_name
FROM student NATURAL JOIN faculty;
Note:
 No commas between table names, just the
key words.

No qualifiers are needed.
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Qualifying Field Names

If a field in the SELECT clause exists in
multiple tables in the FROM clause, you
must qualify the field name by prefacing
it with either table’s name
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Process for Designing
Complex Inner Join Queries
1. Identify all of the tables involved in the
query, and label:



Display fields
Join fields
Search fields
2. Write the query




List
List
List
List
all
all
all
all
display fields in the SELECT clause
table names in the FROM clause
join condition links in the WHERE clause
search fields in the WHERE clause
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Process for Designing
Complex Inner Join Queries
1. What happens if you omit a join
condition in a multiple-table query?
 The output retrieves more rows than
expected. (Cartesian product).
 See example page 166.
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Outer Joins

Limitation of inner joins:


some records may be omitted if
corresponding records don’t exist in one of
the tables
Example:

retrieve records for all students, along with
their corresponding ENROLLMENT
information
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Outer Joins

Student 105 (Michael Connoly) does not have any ENROLLMENT
records. So no information about 105 will be retrieved when
using inner join.
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Outer Joins

No records retrieved for Michael:
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Outer Joins

To include records in first (inner) table,
even when they do not have matching
records in second (outer) table:


place outer join marker (+) beside outer
table name in join clause
The (+) signals the DBMS to insert a NULL
value for the columns in the outer table
that do not have matching rows in the
inner table.
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Outer Joins
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Outer join marker
83
Self Joins

Used to join a table to itself when the table
has a foreign key that references a column in
the same table.
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Self Joins


To create a self-join, you need to create
a table alias, which gives an alternate
name to the table so you can create a
join condition
Syntax to create table alias in FROM
clause:
FROM table1 alias1, table2 alias2
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PARENT_PROJECT
P_ID
Self Joins
PROJECT_NAME
1 Hardware Support Intranet
CLIENT_ID
MGR_ID
PARENT_P_ID
2
105
2 Hardware Support Interface
2
103
1
3 Hardware Support Database
2
102
1
4 T eller Support System
4
105
5 Internet Advertising
6
105
6 Network Design
6
104
7 Exploration Database
5
102
5
SUB_PROJECT
P_ID
PROJECT_NAME
1 Hardware Support Intranet
CLIENT_ID
MGR_ID
PARENT_P_ID
2
105
2 Hardware Support Interface
2
103
1
3 Hardware Support Database
2
102
1
4 T eller Support System
4
105
5 Internet Advertising
6
105
6 Network Design
6
104
7 Exploration Database
5
102
Alias 1
Alias 2
5
PROJECT
P_ID
PROJECT_NAME
1 Hardware Support Intranet
CLIENT_ID
MGR_ID
PARENT_P_ID
2
105
2 Hardware Support Interface
2
103
1
3 Hardware Support Database
2
102
1
4 T eller Support System
4
105
5 Internet Advertising
6
105
6 Network Design
6
104
7 Exploration Database
5
102
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Self Join Example
Note: the table alias is used in the select clause and in join conditions.
NOT the table name.
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Inequality Joins


Join created by placing making join
condition satisfy an inequality
condition(< , > , !=)
Only makes sense when
primary/foreign key values are not
surrogate keys
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Inequality Joins
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Nested Queries

Created when a subquery is nested
within a main query


Main query: first query listed in SELECT
command
Subquery: retrieves one or more values
that specify the main query’s search
condition
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Nested Query Where
Subquery Returns a Single Value

Syntax:
SELECT column1, column2, …
FROM table1, table2, …
WHERE join conditions
AND search_column1 = (SELECT column1
FROM table1, table2, …
Subquery
WHERE search and
that returns
join conditions)
one value
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Nested Query Where
Subquery Returns Multiple Values

Syntax:
SELECT column1, column2, …
FROM table1, table2, …
WHERE join conditions
AND search_column1 IN (SELECT column1
FROM table1, table2, …
Subquery
WHERE search and
that returns
join conditions)
multiple
values
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Using Set Operators in Queries


Performs set operations on outputs of
two unrelated queries
Both queries must have:


same number of display fields
corresponding display fields must have
same data type
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Query Set Operators




UNION: combines results, suppresses
duplicate rows
UNION ALL: combines results, displays
duplicates
INTERSECT: finds matching rows
MINUS: returns the difference between
returned record sets
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Database Views




Logical table based on a query
Does not physically exist in the
database
Presents data in a different format from
underlying tables
Uses:


Security
Simplifying complex queries
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Database Views


Creating a view:
CREATE VIEW view_name AS
SQL_command;
Views can be queried just like tables:
SELECT *
FROM view_name;
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Simple Views


Based on SQL query that retrieves data
from only one table
View can support all table DML
operations:



INSERT
UPDATE
DELETE
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Complex Views


Based on query that retrieves data from
multiple tables
Can only be used to support SELECT
operations

No DML operations supported
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Synonyms


Alternate name for a table
Allows you to not have to preface table
with owner’s username when you are
querying a table that belongs to
another user
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Public Synonyms


Can only be created by a DBA
Syntax:
CREATE PUBLIC SYNONYM synonym_name
FOR owner_name.tablename;

All users with privileges to use table can
then use synonym instead of
owner_name.tablename
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Private Synonyms



You can create private synonyms for
any tables that you have privileges to
use
Only you can use the synonym
Syntax:
CREATE SYNONYM synonym_name
FOR table_name.table_name;
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Dynamic SQL Queries


Queries that allow users to specify
search conditions at runtime
Approaches


Substitution Values
Runtime Variables
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Using Substitution Values


Created when search expression is
prefaced with an ampersand (&)
System then prompts user for value
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Using Runtime Variables

Runtime variable: variable defined
in SQL*Plus environment

Syntax:
DEFINE variable_name = variable_value;

You can then substitute the variable
name for a query search condition
value
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Using Runtime Variables

Example:
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