Enhanced Guide to Oracle 10g

1
Enhanced Guide to Oracle 10g
Chapter 3 Using SQL Queries to Insert, Update,
Delete, and View Data
2
SQL Scripts

• Script text file that contains a sequence of
  SQL commands
• Running a script
• SQLgt START path_to_script_file
• OR
• SQLgt _at_ path_to_script_file
• Path cannot contain any blank spaces

3
Inserting a Value Into EveryField 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 EveryField in a Record

• Example

5
Inserting Selected Table Fields

• Command to insert values for selected record
  fields
• INSERT INTO tablename
• (column1_name, column2_name, )
• VALUES
• (column1_value, column2_value, )

6
Inserting Selected Table Fields

• Example

7
Format 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

8
Inserting Date Values

• Date values must be converted from characters to
  dates using the TO_DATE function and a format
  mask
• Example

9
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'

10
Inserting Interval Values

• Year To Month Interval
• TO_YMINTERVAL(years-months)
• e.g. TO_YMINTERVAL(3-2)
• Day To Second Interval
• TO_DSINTERVAL(days HHMISS.99)
• e.g. TO_DSINTERVAL(-0 011500)

11
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
• 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 SQLPlus
• A transaction ends when you issue either the
  COMMIT or ROLLBACK command
• SQLgtCOMMIT
• SQLgtROLLBACK

13
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

14
Savepoints

• Used to mark individual sections of a transaction
• You can roll back a transaction to a savepoint

15
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

16
Search Conditions

• Format
• WHERE fieldname operator expression
• Operators
• Equal ()
• Greater than, Less than (gt, lt)
• Greater than or Equal to (gt)
• Less than or Equal to (lt)
• Not equal (lt gt, !, )
• LIKE
• BETWEEN
• IN
• NOT IN

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Search Condition Examples

• WHERE s_name Sarah
• WHERE s_age gt 18
• WHERE s_class ltgt SR
• Text in single quotes is case sensitive

18
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 cant delete a record if it contains a
  primary key value that is referenced as a foreign
  key

19
Truncating Tables

• Removes ALL table data WITHOUT saving any
  rollback information
• Advantage fast way to delete table data
• Disadvantage cant be undone
• Syntax
• TRUNCATE TABLE tablename

20
Sequences

• Sequential list of numbers that is automatically
  generated by the database
• Used to generate values for surrogate keys

21
Creating Sequences

• Syntax
• CREATE SEQUENCE sequence_name
• optional parameters
• Example
• CREATE SEQUENCE f_id_sequence
• START WITH 200

22
Viewing Sequence Information

• Query the SEQUENCE Data Dictionary View

23
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

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Pseudocolumn Examples
25
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

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Using PseudocolumnsWith Sequences

• Accessing the next value in a sequence
• sequence_name.NEXTVAL
• Inserting a new record using a sequence
• INSERT INTO my_faculty VALUES
• (f_id_sequence.nextval, Professor Jones)

27
Object Privileges

• 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_name
• TO user1, user 2,
• Revoking object privileges
• REVOKE privilege1, privilege2,
• ON object_name
• FROM user1, user 2,

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Examples of Object Privileges
29
Granting and Revoking Object Privileges
30
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 owners name

33
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

• 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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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

36
Searching for NOT NULL Records

• Use IS NOT NULL operator
• SELECT s_name, s_age
• FROM my_students
• WHERE s_class IS NOT NULL

37
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)

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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)

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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
• _ represents a single wildcard character
• Wildcard characters can be placed at beginning or
  end of string
• Examples
• WHERE s_class LIKE _R
• WHERE s_name LIKE J

41
Sorting Query Output

• Use the ORDER BY clause
• Specify sort key, which is column by which output
  is sorted
• SELECT s_name, s_age
• FROM my_students
• ORDER BY s_age

42
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

43
Using Calculations in Queries

• Arithmetic operations on retrieved data
• Addition ()
• Subtraction (-)
• Multiplication ()
• Division (/)
• Example
• SELECT inv_id, qohprice
• FROM inventory

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Single-RowNumber Functions

• 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

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Using Single-RowNumber Functions

• Example
• SELECT s_name,
• TRUNC((SYSDATE - s_dob)/365)
• FROM my_students

46
Single-RowCharacter 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

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Using Single-RowCharacter 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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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

51
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

52
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

53
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 AVG (s_age) FROM my_students
• SELECT MAX (s_age) FROM my_students
• SELECT MIN (s_age) FROM my_students
• SELECT SUM (s_age) FROM my_students

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Using the GROUP BY Clause

• GROUP BY must be used if some columns in the
  SELECT clause are used in a group function and
  some are not
• Group all fields that are not included in the
  group function
• Example
• SELECT s_class, AVG(s_age)
• FROM my_students
• GROUP BY s_class

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Creating Alternate Column Headings in SQLPlus

• Syntax
• SELECT column1 heading1, column2 heading2,
• Example
• SELECT (SYSDATE s_dob) Student Age
• FROM my_students

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Creating a Column Alias

• Column alias 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

58
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

60
Using Runtime Variables

• Runtime variable variable defined in SQLPlus
  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

62
Formatting Data Using theTO_CHAR Function

• Used to display NUMBER and DATE values using a
  specific format mask
• Syntax
• TO_CHAR(fieldname, format_mask)

63
Join Queries

• Retrieve data from multiple tables by joining
  tables using foreign key references
• Join query types
• Inner (equality)
• Outer
• Self
• Inequality

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Inner Joins
FACULTY

• One record is retrieved for each matching row

65
Inner Joins

• Syntax
• SELECT column1, column2,
• FROM table1, table2
• WHERE table1.join_column
• table2.join_column
• You must include a join condition for every link
  between 2 tables

Join condition
66
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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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 tables name

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Process for DesigningComplex Inner Join Queries

• Identify all of the tables involved in the query,
  and label
• Display fields
• Join fields
• Search fields
• Write the query
• List all display fields in the SELECT clause
• List all table names in the FROM clause
• List all join condition links in the WHERE clause
• List all search fields in the WHERE clause

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Outer Joins

• Limitation of inner joins some records may be
  omitted if corresponding records dont 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

71
Outer Joins

• No records retrieved for Michael

72
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

73
Outer Joins
Outer join marker
74
Self Joins

• Used to join a table to itself when the table has
  a hierarchical relationship

75
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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Self Joins
PARENT_PROJECT
SUB_PROJECT
PROJECT
77
Self Join Example
78
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

79
Inequality Joins
80
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 querys search condition

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Nested Query WhereSubquery Returns a Single Value

• Syntax
• SELECT column1, column2,
• FROM table1, table2,
• WHERE join conditions
• AND search_column1

• (SELECT column1
• FROM table1, table2,
• WHERE search and
• join conditions)

Subquery that returns one value
82
Nested Query WhereSubquery Returns Multiple
Values

• Syntax
• SELECT column1, column2,
• FROM table1, table2,
• WHERE join conditions
• AND search_column1 IN

• (SELECT column1
• FROM table1, table2,
• WHERE search and
• join conditions)

Subquery that returns multiple values
83
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

84
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

85
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

86
Database Views

• Creating a view
• CREATE VIEW view_name AS
• SQL_command
• Views can be queried just like tables
• SELECT
• FROM view_name

87
Simple Views

• Based on SQL query that retrieves data from only
  one table
• View can support all table DML operations
• INSERT
• UPDATE
• DELETE

88
Complex Views

• Based on query that retrieves data from multiple
  tables
• Can only be used to support SELECT operations
• No DML operations supported

89
Synonyms

• Alternate name for a table
• Allows you to not have to preface table with
  owners username when you are querying a table
  that belongs to another user

90
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

91
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