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Chapter 8 (Part b):Chapter 8 (Part b):Advanced SQLAdvanced SQL

Modern Database Modern Database ManagementManagement

99thth Edition EditionJeffrey A. Hoffer, Mary B. Prescott, Jeffrey A. Hoffer, Mary B. Prescott,

Heikki TopiHeikki Topi

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Conditional Expressions Using Conditional Expressions Using Case SyntaxCase Syntax

This is available with This is available with newer versions of newer versions of SQL, previously not SQL, previously not part of the part of the standardstandard

Figure 8-Figure 8-88

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Tips for Developing Tips for Developing QueriesQueries

Be familiar with the data model (entities Be familiar with the data model (entities and relationships)and relationships)

Understand the desired resultsUnderstand the desired results Know the attributes desired in resultKnow the attributes desired in result Identify the entities that contain desired Identify the entities that contain desired

attributesattributes Review ERDReview ERD Construct a WHERE for each linkConstruct a WHERE for each link Fine tune with GROUP BY and HAING Fine tune with GROUP BY and HAING

clauses if neededclauses if needed Consider the effect on unusual dataConsider the effect on unusual data

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Ensuring Transaction Ensuring Transaction IntegrityIntegrity

Transaction = A discrete unit of work Transaction = A discrete unit of work that must be completely processed or that must be completely processed or not processed at allnot processed at all May involve multiple updatesMay involve multiple updates If any update fails, then all other updates If any update fails, then all other updates

must be cancelledmust be cancelled SQL commands for transactionsSQL commands for transactions

BEGIN TRANSACTION/END TRANSACTIONBEGIN TRANSACTION/END TRANSACTION Marks boundaries of a transactionMarks boundaries of a transaction

COMMITCOMMIT Makes all updates permanentMakes all updates permanent

ROLLBACKROLLBACK Cancels updates since the last COMMITCancels updates since the last COMMIT

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Figure 8-9 An SQL Transaction sequence (in pseudocode)

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Data Dictionary FacilitiesData Dictionary Facilities

System tables that store metadataSystem tables that store metadata Users usually can view some of these tablesUsers usually can view some of these tables Users are restricted from updating themUsers are restricted from updating them Some examples in Oracle 10gSome examples in Oracle 10g

DBA_TABLES–descriptions of tablesDBA_TABLES–descriptions of tables DBA_CONSTRAINTS–description of constraintsDBA_CONSTRAINTS–description of constraints DBA_USERS–information about the users of the systemDBA_USERS–information about the users of the system

Examples in Microsoft SQL Server 2000Examples in Microsoft SQL Server 2000 SYSCOLUMNS–table and column definitionsSYSCOLUMNS–table and column definitions SYSDEPENDS–object dependencies based on foreign SYSDEPENDS–object dependencies based on foreign

keyskeys SYSPERMISSIONS–access permissions granted to usersSYSPERMISSIONS–access permissions granted to users

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SQL:1999 and SQL:200SQL:1999 and SQL:200NN Enhancements/ExtensionsEnhancements/Extensions

User-defined data types (UDT)User-defined data types (UDT) Subclasses of standard types or an object typeSubclasses of standard types or an object type

Analytical functions (for OLAP)Analytical functions (for OLAP) CEILING, FLOOR, SQRT, RANK, DENSE_RANKCEILING, FLOOR, SQRT, RANK, DENSE_RANK WINDOW–improved numerical analysis WINDOW–improved numerical analysis

capabilitiescapabilities New Data TypesNew Data Types

BIGINT, MULTISET (collection), XMLBIGINT, MULTISET (collection), XML CREATE TABLE LIKE–create a new table CREATE TABLE LIKE–create a new table

similar to an existing onesimilar to an existing one MERGEMERGE

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Persistent Stored Modules (SQL/PSM)Persistent Stored Modules (SQL/PSM) Capability to create and drop code Capability to create and drop code

modulesmodules New statements:New statements:

CASE, IF, LOOP, FOR, WHILE, etc.CASE, IF, LOOP, FOR, WHILE, etc. Makes SQL into a procedural languageMakes SQL into a procedural language

Oracle has propriety version called Oracle has propriety version called PL/SQL, and Microsoft SQL Server PL/SQL, and Microsoft SQL Server has Transact/SQLhas Transact/SQL

SQL:1999 and SQL:200SQL:1999 and SQL:200NN Enhancements/Extensions Enhancements/Extensions

(cont.)(cont.)

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Routines and TriggersRoutines and Triggers RoutinesRoutines

Program modules that execute on demandProgram modules that execute on demand FunctionsFunctions–routines that return values and –routines that return values and

take input parameterstake input parameters ProceduresProcedures–routines that do not return –routines that do not return

values and can take input or output values and can take input or output parametersparameters

TriggersTriggers Routines that execute in response to a Routines that execute in response to a

database event (INSERT, UPDATE, or database event (INSERT, UPDATE, or DELETE)DELETE)

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Figure 8-10 Triggers contrasted with stored procedures

Procedures are called explicitly

Triggers are event-drivenSource: adapted from Mullins, 1995.

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Figure 8-11 Simplified trigger syntax, SQL:200n

Figure 8-12 Create routine syntax, SQL:200n

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Embedded and Dynamic Embedded and Dynamic SQLSQL

Embedded SQLEmbedded SQL Including hard-coded SQL statements in Including hard-coded SQL statements in

a program written in another language a program written in another language such as C or Javasuch as C or Java

Dynamic SQLDynamic SQL Ability for an application program to Ability for an application program to

generate SQL code on the fly, as the generate SQL code on the fly, as the application is runningapplication is running