1 / 55

Chapter 7

Chapter 7. Introduction to Structured Query Language (SQL). Objectives. Definition of terms Interpret history and role of SQL Define a database using SQL data definition language Write single table queries using SQL Establish referential integrity using SQL

chidi
Télécharger la présentation

Chapter 7

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 7 Introduction to Structured Query Language (SQL) Database Concepts

  2. Objectives • Definition of terms • Interpret history and role of SQL • Define a database using SQL data definition language • Write single table queries using SQL • Establish referential integrity using SQL • Discuss SQL:1999 and SQL:2003 standards Database Concepts

  3. SQL Overview • Structured Query Language • Pronounced Sequel or S-Q-L • The standard for Relational Database Management Systems (RDBMS) • Data management system which implements a relational data model • Data is stored in collection of tables • Data relationships are represented by common values in related tables, not links Database Concepts

  4. History of SQL Database Concepts

  5. Purpose of SQL Standards • Specifies syntax/semantics for data definition and manipulation • Defines data structures and basic operations • For designing, accessing, maintaining, controlling and protecting an SQL database • Enables portability between conforming DBMS’s • Specifies minimal (level 1) and complete (level 2) standards • Provides for later growth/enhancement to standard Database Concepts

  6. Benefits of a Standardized Relational Language • Reduced training costs • Productivity • Application portability • Application longevity • Reduced dependence on a single vendor (nonproprietary) • Cross-system communication Database Concepts

  7. SQL Environment -1 • Catalog • A set of schemas that constitute the description of a database • Schema • The structure that contains descriptions of related objects created by a user (base tables, views, constraints) • Data Definition Language (DDL) • Commands that define a database, including creating, altering, and dropping tables and establishing constraints Database Concepts

  8. SQL Environment -2 • Data Manipulation Language (DML) • Commands that maintain and query a database • Data Control Language (DCL) • Commands that control a database, including administering privileges and committing data Database Concepts

  9. Typical SQL Environment Simplified Schematic As described by the SQL-2003Standard Database Concepts

  10. Some SQL Data types (from Oracle) Database Concepts

  11. Database Development Process DDL DML DCL Database Concepts

  12. SQL Database Definition • Data Definition Language (DDL) • Major CREATE statements: • CREATE SCHEMA • defines a portion of the database owned by a particular user • CREATE TABLE • defines a table and its columns • CREATE VIEW • defines a logical table from one or more views Database Concepts

  13. SQL Database Definition • Other CREATE statements: • CHARACTER SET • Defines a character set for text strings • COLLATION • Specifies the order of the character set • TRANSLATION • Rules that map characters from source CS to a destination CS • ASSERTION • Established a CHECK constraint • DOMAIN • Sets a domain for valid values Database Concepts

  14. Steps in table creation: • Identify data types for attributes • Identify columns that can and cannot be null • Identify columns that must be unique (candidate keys) • Identify primary key-foreign key mates • Determine default values • Identify constraints on columns (domain specifications) • Create the table and associated indexes Table CreationGeneral Syntax forCREATE TABLE Database Concepts

  15. The Enterprise Data Model for Pine Valley Furniture Database Concepts

  16. SQL Database Definition Commands Tables Defined Customer_T Order_T Product_t Order_Line_T Overall table definitions Database Concepts

  17. Defining Attributes and their Data Types Database Concepts

  18. Non-nullable specification Primary keys can never have NULL values Identifying primary key Database Concepts

  19. Primary key Non-nullable specifications Some primary keys are composite – composed of multiple attributes Database Concepts

  20. Controlling the values in attributes Default value Domain constraint Database Concepts

  21. Identifying Foreign Keys and Establishing Relationships Primary key of parent table Foreign key of dependent table Database Concepts

  22. Data Integrity Controls • Referential integrity • constraint that ensures that foreign key values of a table must match primary key values of a related table in 1:M relationships • Restricting: • Deletes of primary records • Updates of primary records • Inserts of dependent records Database Concepts

  23. Ensuring Data Integrity Through Updates Relational integrity is enforced via the primary-key to foreign-key match Database Concepts

  24. Changing and Removing Tables • ALTER TABLE statement allows changes in change column specifications: • ALTER TABLE CUSTOMER_T ADD (TYPE VARCHAR(2)) • DROP TABLE statement removal of tables from schema: • DROP TABLE CUSTOMER_T Database Concepts

  25. Schema Definition • Control processing/storage efficiency: • Choice of indexes • File organizations for base tables • File organizations for indexes • Data clustering • Statistics maintenance • Creating indexes • Speed up random/sequential access to base table data • Example • CREATE INDEX NAME_IDX ON CUSTOMER_T(CUSTOMER_NAME) • This makes an index for the CUSTOMER_NAME field of the CUSTOMER_T table Database Concepts

  26. Insert Statements -1 • Adds data to a table • Inserting into a table • INSERT INTO CUSTOMER_T VALUES (001, ‘Contemporary Casuals’, ‘1355 S. Himes Blvd.’, ‘Gainesville’, ‘FL’, 32601); Database Concepts

  27. Insert Statements -2 • Inserting a record that has some null attributes requires identifying the fields that actually get data • INSERT INTO PRODUCT_T (PRODUCT_ID, PRODUCT_DESCRIPTION, PRODUCT_FINISH, STANDARD_PRICE, PRODUCT_ON_HAND) VALUES (1, ‘End Table’, ‘Cherry’, 175, 8); • Inserting from another table • INSERT INTO CA_CUSTOMER_T SELECT * FROM CUSTOMER_T WHERE STATE = ‘CA’; Database Concepts

  28. Creating Tables with Identity Columns New with SQL:2003 • Inserting into a table does not require explicit customer ID entry or field list • INSERT INTO CUSTOMER_T VALUES ( ‘Contemporary Casuals’, ‘1355 S. Himes Blvd.’, ‘Gainesville’, ‘FL’, 32601); Database Concepts

  29. Delete Statement • Removes rows from a table • Delete certain rows • DELETE FROM CUSTOMER_T WHERE STATE = ‘HI’; • Delete all rows • DELETE FROM CUSTOMER_T; Database Concepts

  30. Update Statement • Modifies data in existing rows • UPDATE PRODUCT_T SET UNIT_PRICE = 775 WHERE PRODUCT_ID = 7; Database Concepts

  31. Merge Statement Makes it easier to update a table…allows combination of Insert and Update in one statement Useful for updating master tables with new data Database Concepts

  32. SELECT List the columns (and expressions) that should be returned from the query FROM Indicate the table(s) or view(s) from which data will be obtained WHERE Indicate the conditions under which a row will be included in the result GROUP BY Indicate categorization of results HAVING Indicate the conditions under which a category (group) will be included ORDER BY Sorts the result according to specified criteria SELECT Statement Used for queries on single or multiple tables Clauses of the SELECT statement: Database Concepts

  33. SQL Statement Processing Order Adapted fromvan der Lans Database Concepts

  34. SQL Examples Database Concepts

  35. SELECT • Find products with standard price less than $275 SELECT PRODUCT_NAME, STANDARD_PRICE FROM PRODUCT_V WHERE STANDARD_PRICE < 275; _V indicates a View where the View isthe Result Database Concepts

  36. SQL Comparison Operators (notice the Not Equal To) Database Concepts

  37. SELECT Using Alias • Alias is an alternative column or table name SELECT CUST.CUSTOMER AS NAME, CUST.CUSTOMER_ADDRESS FROM CUSTOMER_V CUST WHERE NAME = ‘Home Furnishings’; Alias for Customer Name Database Concepts

  38. Using a Function • Using the COUNT aggregate function to find totals SELECT COUNT(*) FROM ORDER_LINE_V WHERE ORDER_ID = 1004; • Note: aggregate functions can’t have single-valued columns included in the SELECT clause • Aggregate functions only produce a one-row answer. • Note differences between COUNT (*) and COUNT Database Concepts

  39. Using Boolean Operators & the Like • AND, OR, and NOT Operators for customizing conditions in WHERE clause • The LIKE operator permits comparing strings using wildcards. • Example • The % wildcard in ‘%Desk’ indicates that all strings that have any number of characters preceding the word “Desk” will be allowed Database Concepts

  40. Using Boolean Operators & Like SELECT PRODUCT_DESCRIPTION, PRODUCT_FINISH, STANDARD_PRICE FROM PRODUCT_V WHERE (PRODUCT_DESCRIPTION LIKE ‘%Desk’ OR PRODUCT_DESCRIPTION LIKE ‘%Table’) AND UNIT_PRICE > 300; Database Concepts

  41. Venn Diagram from Previous Query Database Concepts

  42. Using Ranges SELECT PRODUCT_DESCRIPTION, STANDARD_PRICE FROM PRODUCT_V WHERE STANDARD_PRICE > 199 AND STANDARD_PRICE < 301; Database Concepts

  43. Using Distinct & All • Can only be used once in a SELECT statement SELECT DISTINCT ORDER_ID FROM ORDER_LINE_V; • Returns only one occurrence of each ORDER_ID instead of all occurrences Database Concepts

  44. Sorting Results with the ORDER BY Clause • Sort the results first by STATE, and within a state by CUSTOMER_NAME SELECT CUSTOMER_NAME, CITY, STATE FROM CUSTOMER_V WHERE STATE IN (‘FL’, ‘TX’, ‘CA’, ‘HI’) ORDER BY STATE, CUSTOMER_NAME; Note: the IN operator includes rows whose STATE value is either FL, TX, CA, or HI. It is more efficient than separate OR conditions. NOT IN can also be used. Database Concepts

  45. Categorizing Results Using the GROUP BY Clause • For use with aggregate functions • Scalar aggregate • single value returned from SQL query with aggregate function • Vector aggregate • multiple values returned from SQL query with aggregate function (via GROUP BY) • Note: you can use single-value fields with aggregate functions if they are included in the GROUP BY clause Database Concepts

  46. Categorizing Results Using the GROUP BY Clause SELECT CUSTOMER_STATE, COUNT(CUSTOMER_STATE) FROM CUSTOMER_V GROUPBY CUSTOMER_STATE Database Concepts

  47. Qualifying Results by Categories Using the HAVING Clause with Group By SELECT STATE, COUNT(CUSTOMER_STATE) FROM CUSTOMER_V GROUP BY CUSTOMER_STATE HAVING COUNT(CUSTOMER_STATE) > 1; Like a WHERE clause, but it operates on groups (categories), not on individual rows. Here, only those groups with total numbers greater than 1 will be included in final result Database Concepts

  48. Views Database Concepts

  49. Using and Defining Views • Views provide users controlled access to tables • Base Table • table containing the raw data Database Concepts

  50. Dynamic View A “virtual table” created dynamically upon request by a user No data actually stored; instead data from base table made available to user Based on SQL SELECT statement on base tables or other views Materialized View Copy or replication of data Data actually stored Must be refreshed periodically to match the corresponding base tables Dynamic & Materialized Views Database Concepts

More Related