Skill-building Courses Advance SQL Lesson 6 Normalization & Index

Transcription

1 Skill-building Courses Advance SQL Lesson 6 Normalization & Index

2 Agenda Data collection review Database Normalization Index

3 Data Analysis Process Understand problem Collect Data Analyze Data Interpret Results What questions to ask? What to measure and how to measure? Understand Problem Collect Data What data might help? Where to get the data? What you can do with the data Analyze Data Interpret results What conclusion you can get form the analysis

4 Database Normalization Cust_ID Customer_Name Customer Address Cust_Addr_Type Cust_Acct_1 Acct_Type_1 Acct_Branch_1 Cust_Acct_2 Acct_type_2 Acct_Branch_ Riannon Rey th Ave, Forest Hills, NY, US, Physical Checking NY Savings NY Rorie Lucas 367 Westwood Avenue, Hicksville, NY, US, Physical Savings NY Kaelyn Johnson nd St, Forest Hills, NY, US, Physical Checking NY Robina Scrivens 3056 West Side Avenue, Jersey City, NJ, US, Physical Checking NJ Savings NY Ferdie Clifton 4069 Ferry Street, Jersey City, NJ, US, Physical Checking NJ Ferdie Clifton 4069 Ferry Street, Jersey City, NJ, US, Mailing Checking NJ001 Think about: Update the branch NY001 Add a new branch NY002 Add an account for customer Riannon Rey Add mailing address of customer Karelyn Johnson Delete customer information of Rorie Lucas

5 Database Normalization The objectives of normalization Design good table structures and minimize redesign when extending the database structure Reduce redundancy Avoid data anomalies Insertion Insert extra data Update Change multiple rows to modify a single fact Deletion Cause data lost Ensure data dependency make sense

6 Database Normalization List of Common Normal Forms Unnormalized form (UNF) First normal form (1NF) Second normal form (2NF) Third normal form (3NF)

7 Database Normalization UNF 1NF Each Column contains atomic values Removing repeating groups Each table has primary key to ensure the row is unique Cust_First Cust_Las Cust_Addr_ Cust_Ad Cust_Add Cust_Ad Cust_Ad Cust_ID _Name t_name Cust_Addr City dr_state r_country dr_zip dr_type Cust_Acct Acct_Type Acct_Branch Riannon Rey th Ave Forest Hills NY US Physical Checking NY Riannon Rey th Ave Forest Hills NY US Physical Savings NY Rorie Lucas 367 Westwood Avenue Hicksville NY US Physical Savings NY Kaelyn Uccello nd St Forest Hills NY US Physical Checking NY Robina Scrivens 3056 West Side Avenue Jersey City NJ US Physical Checking NJ Robina Scrivens 3056 West Side Avenue Jersey City NJ US Physical Savings NY Ferdie Clifton 4069 Ferry Street Jersey City NJ US Physical Checking NJ Ferdie Clifton 494 Ocean Street Little Neck NY US Mailing Checking NJ001

8 Database Normalization 1NF 2NF Every non-primary key attribute is fully functionally dependent on the primary key (Remove Partial Dependency) Cust_ID (PK) Cust_First_Name Cust_Last_Name Riannon Rey Rorie Lucas Kaelyn Uccello Robina Scrivens Ferdie Clifton Acct_ID(PK) Cust_ID(FK) Cust_Acct Acct_Type Acct_Branch Checking NY Savings NY Savings NY Checking NY Checking NJ Savings NY Checking NJ001 Addr_ID(PK) Cust_ID(FK) Cust_Addr Cust_Addr_City Cust_Addr_State Cust_Addr_Country Cust_Addr_Zip Cust_Addr_Type th Ave Forest Hills NY US Physical Westwood Avenue Hicksville NY US Physical nd St Forest Hills NY US Physical West Side Avenue Jersey City NJ US Physical Ferry Street Jersey City NJ US Physical Ocean Street Little Neck NY US Mailing

9 Function Dependency The value of one attribute (the determinant) determines the values of another attribute A->B A B is functionally depended on A B Example: Primary Key determines all non-key fields in the table Cust_ID -> Cust_First_Name, Cust_Last_Name

10 Partial Dependency AB -> C A -> C Example: Cust_ID, Acct_ID -> Customer_Name Cust_ID -> Customer_Name

11 Database Normalization 2NF 3NF Every non-key attribute is non-transitively dependent on the Primary key (Remove transitive dependency) Acct_ID(PK) Cust_ID(FK) Cust_Acct Cust_Acct_Type Acct_Branch Branch_Address Branch_Manager Checking NY-Forest Hills st Ave, Forest Hill, NY, Lydia Dawson Savings NY-Forest Hills st Ave, Forest Hill, NY, Lydia Dawson Savings NY-High Bridge Forest Park Street, High Bridge, NY Lynne Henderson Checking NY-Forest Hills st Ave, Forest Hill, NY, Lydia Dawson Checking NJ-Jersey City Grove Street, Jersey City, NJ, Philip Weber Savings NY-Williamsburg Hope Street, Williamsburg, NY, Taylor Todd Checking NJ-Jersey City Grove Street, Jersey City, NJ, Philip Weber Branch_ID(PK) Branch_Name Branch_Address Branch_Manager 001 NY-Forest Hills st Ave, Forest Hill, NY, Lydia Dawson 002 NY-High Bridge Forest Park Street, High Bridge, NY Lynne Henderson 003 NJ-Jersey City Grove Street, Jersey City, NJ, Philip Weber 004 NY-Williamsburg Hope Street, Williamsburg, NY, Taylor Todd Acct_ID(PK) Cust_ID(FK) Cust_Acct Acct_Type Acct_Branch Checking NY Savings NY Savings NY Checking NY Checking NJ Savings NY Checking NJ001

12 Transitive Dependency A -> B B -> C Example: Cust_ID -> Acct_ID Acct_ID -> Acct_Type

13 Database Normalization Some Tips Understand the business requirement when design tables Identify entity and understand function dependencies in the data Every table must have primary key Higher normal form may not desirable Complexity Performance issue

14 CitiBike Data tripduration starttime stoptime start station id start station name start station latitude start station longitude end station id end station name end station latitude end station longitude bikeid usertype birth year gender /1/2015 0:01 1/1/2015 0: Ave & E 44 St Stanton St & Chrystie St Subscriber /1/2015 0:02 1/1/2015 0: Ave & W 18 St W 15 St & 7 Ave Subscriber /1/2015 0:04 1/1/2015 0: E 24 St & Park Ave S Ave & W 33 St Subscriber /1/2015 0:04 1/1/2015 0: Fulton St & Waverly Ave Lafayette Ave & St James Pl Subscriber /1/2015 0:05 1/1/2015 0: Ave & E 29 St E 7 St & Avenue A Subscriber /1/2015 0:07 1/1/2015 0: W 29 St & 9 Ave Greenwich Ave & Charles St Subscriber /1/2015 0:07 1/1/2015 0: Broadway & W 32 St Ave & E 29 St Subscriber /1/2015 0:08 1/1/2015 0: Washington St & Gansevoort St E 25 St & 1 Ave Subscriber /1/2015 0:09 1/1/2015 0: W 49 St & 8 Ave W 39 St & 9 Ave Subscriber /1/2015 0:10 1/1/2015 0: E 37 St & Lexington Ave E 25 St & 1 Ave Subscriber /1/2015 0:10 1/1/2015 0: Madison St & Montgomery St Cleveland Pl & Spring St Subscriber /1/2015 0:11 1/1/2015 0: Pershing Square South Lexington Ave & E 26 St Subscriber /1/2015 0:13 1/1/2015 0: Ave & E 58 St E 25 St & 2 Ave Subscriber /1/2015 0:13 1/1/2015 0: Allen St & Hester St St Marks Pl & 1 Ave Subscriber /1/2015 0:14 1/1/2015 0: E 6 St & Avenue B E 27 St & 1 Ave Subscriber /1/2015 0:14 1/1/2015 0: W 39 St & 9 Ave Ave & W 18 St Subscriber /1/2015 0:14 1/1/2015 0: Broadway & E 14 St Allen St & E Houston St Subscriber /1/2015 0:16 1/1/2015 0: W 25 St & 6 Ave E 51 St & 1 Ave Subscriber /1/2015 0:17 1/1/2015 0: William St & Pine St Clark St & Henry St Subscriber /1/2015 0:18 1/1/2015 0: W 37 St & 5 Ave Mott St & Prince St Subscriber /1/2015 0:18 1/1/2015 0: W 52 St & 9 Ave Ave & W 22 St Subscriber /1/2015 0:18 1/1/2015 0: Ave & E 29 St E 31 St & 3 Ave Subscriber

15 Entity Relationship Diagram (ERD)

16 Index A database index is a data structure that improves the speed of data retrieval operations on a database table at the cost of additional writes and storage space to maintain the index data structure.

17 Cluster Index Sort and store the data rows in the table or view based on their key values. Only one Cluster Index per table Level 2 Customer ID (Cluster Index) Level 1 Customer ID (Cluster Index) Customer ID (Cluster Index) Level 0 Customer Details for Customer ID Customer Details for Customer ID Customer Details for Customer ID Customer Details for Customer ID

18 Non Cluster Index Separate structure from the actual data rows of the table. The key value has a pointer to the data row Multiple Indexes per table Customer ID Row Locator

19 Index Rules for using Indexes Use on larger tables Index search fields (fields frequently in WHERE clause) Index fields frequently used in SQL ORDER BY and GROUP BY commands Limit the use of indexes for volatile databases (Modification such as inserts, delete, and updates require updates in index files as well)

20 Create Index SQL Syntax Create a nonclustered index on a table or view CREATE INDEX indexname ON tablename (ColunmName) Create a clustered index on a table CREATE CLUSTERED INDEX IndexName ON TableName (ColumnName)

21 Homework Design a database model for Citi Bike and create a Entity Relationship Diagram (Free to make your own assumptions) Create the tables in database and build the index

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