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Module 7:Modifying Data

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Overview

Using Transactions

Inserting Data

Deleting Data Updating Data

Performance Considerations

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Using Transactions

StartingTransactions

Explicit

Autocommit

Implicit

Ending Transactions

COMMIT statement

ROLLBACK

statement

BEGIN TRANSACTION

UPDATE savings

. . .

UPDATE checking

. . .

COMMIT TRANSACTION

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Inserting Data

Inserting a Row of Data by Values

Using the INSERTSELECT Statement

Creating a Table Using the SELECTINTO Statement

Inserting Partial Data

Inserting Data by Using ColumnDefaults

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Inserting a Row of Data by Values

Must Adhere to DestinationConstraints or theINSERT Transaction Fails

Use a Column List to SpecifyDestination Columns

Specify a Corresponding List of Values

USE northwind

INSERT customers

(customerid, companyname, contactname, contacttitle

,address, city, region, postalcode, country, phone

,fax)

VALUES ('PECOF', 'Pecos Coffee Company', 'Michael Dunn'

,'Owner', '1900 Oak Street', 'Vancouver', 'BC'

,'V3F 2K1', 'Canada', '(604) 555-3392'

,'(604) 555-7293')

GO

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USE northwind

INSERT customers

SELECT substring(firstname, 1, 3)+ substring (lastname, 1, 2)

,lastname, firstname, title, address, city

,region, postalcode, country, homephone, NULL

FROM employees

GO

Using the INSERTSELECTStatement

All Rows That Satisfy the SELECTStatement Are Inserted

Verify That the Table That ReceivesNew Row Exists

Ensure That Data Types Are Compatible

Determine Whether Default ValuesExist or Whether Null Values AreAllowed

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Creating a Table Using the SELECTINTO Statement

Use to Create a Table and Insert Rowsinto the Tablein a Single Operation

Create a Local or Global TemporaryTable

Create Column Alias or SpecifyColumn Names in the Select List forNew TableUSE northwind

SELECT productname AS products

,unitprice AS price

,(unitprice * 1.1) AS taxINTO #pricetable

FROM products

GO

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Inserting Partial Data

USE northwind

INSERT shippers (companyname)

VALUES ('Fitch & Mather')

GO

Adding new data

USE northwind

SELECT *

FROM shippers

WHERE companyname = 'Fitch & Mather'

GO

Verifying new data

shipperidshipperid

37

companynamecompanyname

Fitch & Mather

phonephone

Null

Allows Null Values

Example 1

Example 2

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Inserting Data by Using ColumnDefaults

DEFAULT Keyword

Inserts default values for specifiedcolumns

Columns must have a default value orallow null values

DEFAULT VALUES Keyword

Inserts default values for all columns

Columns must have a default value orallow null values

USE northwind

INSERT shippers (companyname, phone)

VALUES ('Kenya Coffee Co.', DEFAULT)

GO

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Deleting Data

Using the DELETE Statement

Using the TRUNCATE TABLE Statement

Deleting Rows Based on Other Tables

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Using the DELETE Statement

The DELETE statement removes one ormore rows in a table according to theWHERE clause condition, if specified

Each Deleted Row Is Logged in theTransaction Log

USE northwind

DELETE orders

WHERE DATEDIFF(MONTH, shippeddate, GETDATE()) >= 6GO

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USE northwind

TRUNCATE TABLE orders

GO

Using the TRUNCATE TABLEStatement

The TRUNCATE TABLE StatementDeletes All Rowsin a Table

SQL Server Retains Table Structureand Associated Objects

Only Deallocation of Data Pages IsLogged in the Transaction Log

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Deleting Rows Based on OtherTables

Using an Additional FROM Clause

First FROM clause indicates table tomodify

Second FROM clause specifies restrictingcriteria for the DELETE statement

Specifying Conditions in the WHERE

Clause Subqueries determine which rows to

delete

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Updating Data

Updating Rows Based on Data in theTable

Updating Rows Based on Other Tables

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USE northwindUPDATE products

SET unitprice = (unitprice * 1.1)

GO

Updating Rows Based on Data in theTable

WHERE Clause Specifies Rows toChange

SET Keyword Specifies the New Data

Input values must have compatibledata types with the columns

Updates Do Not Occur in Rows ThatViolate Any Integrity Constraints

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Updating Rows Based on OtherTables

How the UPDATE Statement Works

Never updates the same row twice

Requires table prefixes on ambiguouscolumn names

Specifying Rows to Update Using Joins

Uses the FROM clause

Specifying Rows to Update UsingSubqueries

Correlates the subquery with the

updated table

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Performance Considerations

All Data Modifications Occur Within aTransaction

Data Page Allocation May Occur

Modifying Indexed Data IncursAdditional Overhead

Indexes Can Assist Search Criteria

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Recommended Practices

Always Write a SELECT Statement That Does Not ModiData Before You Actually Modify Data

Improve the Readability of a Result Set by Changing

Column Names or by Using Literals

Always Include a WHERE Clause with the DELETE anUPDATE Statements

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Lab A: Modifying Data

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Review

Using Transactions

Inserting Data

Deleting Data Updating Data

Performance Considerations