1. CS122 Using Relational Databases and SQL
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CS122 Using Relational Databases and SQL
8. Data Manipulation and Definition
Randy Moss
Department of Computer Science
California State University, Los Angeles 1

2. Outline Data manipulation Data definition INSERT DELETE UPDATE
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Outline
Data manipulation
INSERT
DELETE
UPDATE
Data definition
CREATE a table
MODIFY a table
DELETE a table
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3. Insert Adds new records to a table Two general forms of the syntax
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Insert
Adds new records to a table
Two general forms of the syntax
One adds a single new record using specific values
The other is for inserting one or more records using the results of a query
Two parts to statement
First part lists table and the fields that will receive the data
Second part specifies values to be inserted into the table

4. Insert one record Two general forms of the syntax
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Insert one record
Two general forms of the syntax
INSERT INTO table VALUES ( value1, value2, … )
INSERT INTO table (field [, …] ) VALUES ( value [, …] );
Make sure the order of the values matches the order of the field
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5. Example 1 Add 'Hip-Hop' as a new genre in the Genre table
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Example 1
Add 'Hip-Hop' as a new genre in the Genre table
INSERT INTO Genre
VALUES ('hip-hop')
INSERT INTO Genre (genre)
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Example 2
Add new title as TitleID 8 recorded by Word (ArtistID 3) called 'Word Live', recorded in StudioID 2 in the genre 'pop‘.
Insert into Titles Values(8,3,'Word Live',2,
' ','pop')
Insert into Titles(TitleID,ArtistID,Title,StudioID,Upc,Genre) Values(8,3,'Word Live',2, ' ','pop')
The upc of the new record is ‘ ‘
Commas separating fields
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7. The upc of the new record is NULL
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Example 2 (Cont.)
Insert into Titles Values(8,3,'Word Live',2,
NULL ,'pop')
The upc of the new record is NULL
Insert into Titles(TitleID,ArtistID,Title,StudioID,Genre) Values(8,3,'Word Live',2,'pop')
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8. Insert Rules Must supply values to all fields except:
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Insert Rules
Must supply values to all fields except:
Those that can have null values
Those that auto-generate
Those with default values
To explicitly insert a Null value, use the word Null without quotes
Cannot use two commas together with nothing between them
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9. INSERT using a query Two general forms of the syntax
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INSERT using a query
Two general forms of the syntax
INSERT INTO table select_query;
INSERT INTO table ( field [, …] ) select_query
Can insert multiple records
Follow field list with valid SQL SELECT that produces data for field list
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Example 1
Populate the AudioFiles table with all the MP3s from the Tracks table
Insert into Audiofiles(TitleID, Tracknum, AudioFormat)
Select TitleID, Tracknum, 'mp3' From Tracks Where MP3 = 1
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Example 2
Add a new salesperson as SalesID 6, named ‘Courtney Mulligan’ with initials of ‘cgm’, a base salary of 200, and supervised by ‘Bob Bentley’
INSERT INTO SalesPeople (SalesID, Firstname, Lastname, Initials, Base, Supervisor)
SELECT 6, 'Courtney','Mulligan','cgm',200, SalesID
FROM SalesPeople
WHERE Firstname = 'Bob' And Lastname='Bentley'
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12. Comments Just follow the field list with a SELECT statement.
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Comments
Just follow the field list with a SELECT statement.
The SELECT clause must produce the same number of columns
In the same order
With the same datatype
If the field list is omitted, select all the fields of the table
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13. DELETE Syntax DELETE FROM table WHERE condition(s);
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DELETE
Syntax
DELETE FROM table
WHERE condition(s);
Delete one or more rows
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14. Generally delete on primary key
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Example 1
Delete the salesperson with SalesID 6.
Delete From SalesPeople
Where SalesID=6
Generally delete on primary key
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15. Cannot use Join in delete
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Example 2
Delete all records in the Audiofiles table related to the CD ‘Time Flies’
Delete From Audiofiles
Where TitleID IN (Select TitleID
From Titles
Where Title='Time Flies')
Cannot use Join in delete
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16. Update
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Syntax in simplest form is to specify the table to be updated followed by SET and field=value
If setting multiple values, use SET only once and separate each field=value pair with a comma
The value that you set the field(s) to can be:
A specific value
The old value with new information added
The result of a mathematical calculation
Value from another field
Use WHERE clause to specify which records to change

17. UPDATE (Single table) Syntax UPDATE table
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UPDATE (Single table)
Syntax
UPDATE table
SET field1=value1, field2=value2
WHERE condition(s);
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18. Example 1 Give salesperson Bob Bentley a $50 raise in Base
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Example 1
Give salesperson Bob Bentley a $50 raise in Base
Update SalesPeople
Set Base=Base+50
Where Firstname='Bob' And
Lastname = 'Bentley'
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Example 2
Member Frank Payne works from his home. Set his workphone number to the value of his homephone number.
Update Members
Set Workphone=Homephone
Where Firstname='Frank' And
Lastname='Payne'
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Example 3
Change the record for the title ‘Time Flies’ to set the UPC to and the Genre to 'pop‘
Update Titles
Set UPC=' ', Genre='pop'
Where Title='Time Flies'
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21. UPDATE (Multiple table)
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UPDATE (Multiple table)
Update Table1, Table2
Set Field = Value, field = value
Where Table1.field=Table2.field
AND Condition
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Example 1
All the members of the group Confused now have e- mail addresses that are the member's firstname followed by Update the members.
Update Members M, XrefArtistsMembers X, Artists A
Set = Concat(M.firstname
Where M.MemberID = X.MemberID
AND A.ArtistID = X.ArtistID
AND Artistname = 'Confused'
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Example 2
All members in Virginia who have previously been handled by Scott Bull will now be handled by Clint Sanchez, whose salesID is 3.
Update Members M, SalesPeople S
Set M.SalesID=1
Where M.SalesID=S.SalesID
AND Region='VA'
AND S.Firstname='Clint'
AND S.Lastname='Sanchez'
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24. Transactions Suppose you want to add a new CD title and its tracks
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Transactions
Suppose you want to add a new CD title and its tracks
Need to insert a record to titles
Need to insert multiple records to tracks
What if we did part of those inserts and not all of them?
Result would be an incomplete data
Transactions let you group individual commands and require that they are all completed or not completed as a group
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25. Formal Definition of Transaction
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Formal Definition of Transaction
A logical unit of work made up of a series of statements:
Selects, inserts, updates, or deletes
No errors = ALL modifications are accepted
Errors = NO modifications are accepted
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26. ACID Properties of Transactions
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ACID Properties of Transactions
Atomicity
Consistency
Isolation
Durability
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ACID continued
Atomicity guarantees that a transaction must either be completely done, or not at all.
Consistency:
The details and totals match
No orphan data exists
Isolation means that no other user sees any part of the transaction until it is all completed
Durability says that when the transaction is finished, the data will persist and be saved.
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28. ACID example Bank Transaction:
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ACID example
Bank Transaction:
Atomicity: if you cancel your transaction in the middle of doing it, it will be fully cancelled
Consistency: Depositing to two accounts should subtract from main account twice, not once.
Isolation: Bank transactions should happen one after the other to avoid consistency issue above.
Durability: My money stays in my account after I leave.
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29. Transaction Syntax BEGIN TRANSACTION;
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Transaction Syntax
BEGIN TRANSACTION;
DELETE FROM Tracks WHERE TitleID = 44;
DELETE FROM Titles WHERE TitleID = 44;
COMMIT;
#Or rollback if there are any errors
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30. Concurrency Issues Dirty reads (Uncommitted dependency)
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Concurrency Issues
Dirty reads (Uncommitted dependency)
One user reads a record that is part of another user's incomplete transaction
Unrepeatable reads (Inconsistent Analysis)
A record is read twice during a transaction, and the second read is affected by a separate transaction
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31. Concurrency Issues Continued
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Concurrency Issues Continued
Phantoms
One user may be updating all the records in a table at the same time another user is inserting a new record to the table
Lost updates
Two transaction try to update the same record
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32. Locks to the Rescue! Automatic locking by database Record locking
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Locks to the Rescue!
Automatic locking by database
Record locking
Page locking
Table locking
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33. Even Locks Have Problems…
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Even Locks Have Problems…
Deadlock:
Two transactions each waiting for each other to complete
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34. Preventing Deadlocks Always update table in the same order
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Preventing Deadlocks
Always update table in the same order
Keep transactions as short as possible
Do not place user interaction in the middle of transaction
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