Module 3 Designing a Physical Database Model

Module Overview Selecting Data Types Designing Database Tables Designing Data Integrity

Lesson 1: Selecting Data Types Considerations for Selecting Standard Column Data Types Considerations for Selecting New SQL Server 2008 Data Types Considerations for Using CLR User-Defined Data Types Considerations for Using Spatial Data Types Guidelines for Using the XML Data Type Establishing Naming Standards for Database Objects Discussion: Working with Data Tables

Considerations for Selecting Standard Column Data Types Integer versus GUID primary keys Fixed versus variable length columns VARCHAR (MAX), NVARCHAR (MAX), and VARBINARY (MAX) data types Character column collations and Unicode and non-Unicode data types Transact-SQL user-defined data types

Considerations for Selecting New SQL Server 2008 Data Types Same date precision as date Same time precision as time DateTimeOffset is time zone aware Same date precision as date Same time precision as time DateTimeOffset is time zone aware Datetime2 / Datetimeoffset When a table contains a FILESTREAM column When objects are larger than 1 MB Where fast read access is important Where you use a middle tier When a table contains a FILESTREAM column When objects are larger than 1 MB Where fast read access is important Where you use a middle tier FILESTREAM Date: From 01/01/0001 to 12/31/9999 Date: No time component Time: Based on 24 hour clock, NO date component Time: Accurate to 100 ns Date: From 01/01/0001 to 12/31/9999 Date: No time component Time: Based on 24 hour clock, NO date component Time: Accurate to 100 ns Date / Time To create tables with a hierarchical structure To query and perform work with hierarchical data by using T-SQL To create tables with a hierarchical structure To query and perform work with hierarchical data by using T-SQL Hierarchyid

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Considerations for Using CLR User-Defined Data Types Use common language runtime (CLR) user-defined data types for nonstandard or proprietary data types Avoid excessively complex data types Consider the risks of tightly coupling a CLR user-defined data types and the database Consider the overhead of row-by-row processing

Considerations for Using Spatial Data Types Spatial Data: Represents information on the location and shape of geometric objects Can be of two types including geometry and geography data types Implemented as.NET common language runtime data types in SQL Server Supports eleven spatial data objects, or instance types Represents information on the location and shape of geometric objects Can be of two types including geometry and geography data types Implemented as.NET common language runtime data types in SQL Server Supports eleven spatial data objects, or instance types Spatial Data Geometry Data Type Geography Data Type

Guidelines for Using the XML Data Type Use the XML data type for data that is not frequently updated Use typed XML columns Use the XML data type for data that is not relationally structured Use the XML data type for configuration information Use the XML data type for data with recursive structures

Establishing Naming Standards for Database Objects Use only standard abbreviations in names Use names that comply with the rules for forming SQL Server 2008 identifiers Use descriptive terms Use models for naming standards Be consistent across all objects Record and communicate naming standards Use prefixes ONLY when it provides value Use policy-based management Name intersection tables consistently

Discussion: Working with Data Tables Scenario: Some developers argue to use a simple table structure containing only four columns—a unique row identifier, a field identifier (analogous to a column name), a datatype indicator, and the data itself stored as a sqlvariant. Some say that the application could reconstitute all data fields, and pivot them into a virtual table. The argument often goes further to whether developers should be involved in working with the database schema, since they can create new data properties (fields) as needed. Question: What is the fallacy in these arguments?

Guidelines for Determining Table Width What Are Sparse Columns? Demonstration: How To Create a Table By Using Sparse Columns Guidelines for Using Computed Columns Discussion: Using Computed Columns Lesson 2: Designing Database Tables

Guidelines for Determining Table Width Large Object Types Data Overflow Capacity Planning

Properties of Sparse Columns What Are Sparse Columns? The SQL Server Database Engine uses the SPARSE keyword in a column definition to optimize the storage of values in that column. Catalog views for a table that has sparse columns are the same as for a typical table. The COLUMNS_UPDATED function returns a varbinary value to indicate all the columns that were updated during a DML action. The SQL Server Database Engine uses the SPARSE keyword in a column definition to optimize the storage of values in that column. Catalog views for a table that has sparse columns are the same as for a typical table. The COLUMNS_UPDATED function returns a varbinary value to indicate all the columns that were updated during a DML action. Sparse columns are ordinary columns that have an optimized storage for NULL values. They can be used with column sets and filtered index. Data types that you cannot specify as sparse are geography, geometry, image, ntext, text, timestamp, and user-defined data types.

Demonstration: How To Create a Table By Using Sparse Columns In this demonstration, you will see how to: Create a table by using sparse columns

Avoid the overhead of complex functions in computed columns Avoid persisted computed columns on active data Protect against numeric overflow and divide by zero errors Use persisted computed columns for performance Guidelines for Using Computed Columns Use computed columns to derive results from other columns Usage of Computed Columns Exceptions in Column Data Usage of Persisted Computed Columns Usage of Computed Columns Exceptions in Column Data Computed Columns

Discussion: Using Computed Columns What kind of problems do computed columns solve? When is a computed column actually computed?

Lesson 3: Designing Data Integrity Guidelines for Designing Column Constraints Guidelines for Designing Table Constraints Guidelines When Implementing DDL Triggers Discussion: Identifying the Best Options for Column Data Types and Data Constraints

Guidelines for Designing Column Constraints Use column CHECK Constraints CONSTRAINT chkQty CHECK (Amount > 0)...) Declare columns as NOT NULL (HireDate int NOT NULL...) Use ANSI default constraints (CONSTRAINT Qty DEFAULT 0...) Use CHECK constraints instead of bound rules Check Constraint Bound Rules

Guidelines for Designing Table Constraints Use DRI for data integrity in a database Use triggers to enforce referential integrity Use ANSI-standard options Use table-level CHECK constraints Check Constraint ON DELETE Specify cascading levels and options

Guidelines for Designing Database Constraints by Using DDL Triggers Use DDL triggers for auditing Use DDL triggers to prevent database changes Use DDL triggers to support security

Guidelines When Implementing DDL Triggers Use DDL triggers with transactions Use DDL triggers scope to control database operations or objects that activates the trigger Avoid creating DDL Trigger on both CREATE_SCHEMA and CREATE_TABLE event Use value() instead of query() when querying data returned from EVENTDATA

Discussion: Identifying the Best Options for Column Data Types and Data Constraints Scenario: QuantamCorp is a local company conducting business only in USA and Canada. You need to create a single table to contain the following information. 1. Time of the day for a 24 hour clock 2. Company name 3. address 4. Postal code 5. Product information 6. Product descriptive brochure 7. Telephone number Question: What are the best options for column data types and data constraints?

Lab 3: Designing a Physical Database Model Exercise 1: Specifying Database Object Naming Standards Exercise 2: Converting a Logical Database Model into a Physical Database Model Estimated time: 40 minutes Logon Information Virtual machine User name Password NYC-SQL1 Administrator Pa$$w0rd

Lab Scenario The main goals of the HR VASE project are as follows: Provide managers with current and historical information about employee vacation and sick-leave data. Provide permission to individual employees to view their vacation and sick-leave balances. Provide permission to selected employees in the HR department to view and update employee vacation and sick-leave data. Provide permission to the HR manager to view and update all the data. Standardize employee job titles. In this lab, you will build a physical database model based on the logical model created earlier. You are a lead database designer at QuantamCorp. You are working on the Human Resources Vacation and Sick Leave Enhancement (HR VASE) project that is designed to enhance the current HR system of your organization. This system is based on the QuantamCorp2008 sample database in SQL Server 2008.

Lab Review Can you explain the purpose of creating naming standards and having a Naming Standards policy? What kind of issues may arise if a Naming Standards policy does not exist?

Module Review and Takeaways Review Questions Real-world Issues and Scenarios

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