Oracle SQL Basics by Ankur Raina


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This is an introductory course to Oracle SQL.

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Oracle SQL Basics by Ankur Raina

  1. 1. 2011ANKUR Contacts: E-mail: Phone: 9813269824RAINA[ORACLE DATABASEPRESENTATION FOR THEBASIC SQL UNDERSTANDING]All the rights are reserved with the author. No part of this publication may be changed in any formwithout the prior permission of the author. Copyright 2011
  2. 2. CONTENTS 1. Introduction to Oracle RDBMS 3 1.1.Features 3 1.2.Oracle Internet Platform 4 2. E.F.Codd’s Rules 5 2.1 Rules 5 2.2 Satisfied by Oracle RDBMS 6 3. Oracle Database Architecture 8 3.1. The Database 9 3.2. The Instance 11 4. SQL Statements 14 4.1.Types 14 4.2. Capabilities of SQL SELECT Statements 15 4.3.Data Retrieval Using SELECT Statement 15 4.4.Defining a NULL value 16 4.5.Defining a Column Alias 17 4.6.Restricting and Sorting Statements 17 5. Using Single Row Functions To Customize Output 18 5.1. Features 22 5.2. General Functions 22 5.3. CASE Expression 24 5.4. DECODE Function 25 6. Reporting Aggregating Data Using Group Functions 26 6.1. Group Function 26 6.2. Creating Groups of Data: GROUP BY clause syntax 27 6.3. Using GROUP BY clause for multiple columns 28 6.4. Restricting Group Results by HAVING clause 28 7. Displaying Data From Multiple Tables 29 7.1 Using Subqueries to Solve Queries 30ANKUR RAINA 09-IT-4505
  3. 3. 8. Manipulating Data 31 8.1. INSERT statement 31 8.2. UPDATE statement 32 8.3. DELETE statement 32 8.4. TRUNCATE statement 32 9. Database Objects 34 9.1. CREATE statement 34 9.2. CREATE TABLE using a sub-query 35 9.3. Dropping a table 35 10.Creating Other Schema Objects 36 10.1. Views 36 10.2.Creating views 36 10.3.Sequence 37 10.4.Indexes 37 10.5.Synonyms 38 11.References 39ANKUR RAINA 09-IT-4505
  4. 4. CHAPTER 1 “Our goal is very simply to become the desktop for e-businesses - Larry Ellison”Introduction to Oracle RDBMSThe Oracle Database (commonly referred to as Oracle RDBMS or simply as Oracle) is anobject-relational database management system (ORDBMS) produced and marketed byOracle Corporation. Larry Ellison and his friends and former co-workers Bob Miner and EdOates started the consultancy Software Development Laboratories (SDL) in 1977. SDLdeveloped the original version of the Oracle software. The name Oracle comes from thecode-name of a CIA-funded project Ellison had worked on while previously employed byAmpex. The latest release of Oracle RDBMS is 11g Release 2.Features:-ANKUR RAINA 09-IT-4505
  5. 5. Oracle Internet Platform The Oracle products provide all the necessary components to develop an application. The integrated Oracle Internet Platform includes everything needed to develop, deploy, and manage internet applications, including these three core pieces: 1. Browser-based clients to process presentation 2. Application servers to execute business logic and serve presentation logic to browser-based clients 3. Databases to execute database-intensive business logic and serve dataANKUR RAINA 09-IT-4505
  6. 6. CHAPTER 2E.F.Codd’s RulesE.F. Codd, the famous mathematician has introduced 12 rules for the relational model fordatabases commonly known as Codds rules. The rules mainly define what is required for aDBMS for it to be considered relational, i.e., an RDBMS. There is also one more rule i.e.Rule00 which specifies the relational model should use the relational way to manage thedatabase. The rules and their description are as follows:-Rules:Rule 000: Zeroth rule:An RDBMS system should be capable of using its relational facilities (exclusively) to managethe database.Rule 1: The information rule:All information in the database is to be represented in one and only one way. This isachieved by values in column positions within rows of tables.Rule 2: The guaranteed access rule:All data must be accessible with no ambiguity. This is achieved in the RDBMS by using theprimary key concept.Rule 3: Systematic treatment of null values:The DBMS must allow each field to remain null. The null can be stored in any field of anydatatype.Rule 4: Active online catalog based on the relational model:The authorized users can access the database structure by using common language i.e. SQL.Rule 5: The comprehensive data sublanguage rule:The system must support at least one relational language that has simple syntax andtransaction management facilities. It can be used in the application as well as in the RDBMSsystems.ANKUR RAINA 09-IT-4505
  7. 7. Rule 6: The view updating rule:All views must be updatable by the system.Rule 7: High-level insert, update, and delete:The system is able to insert, update and delete operations fully. It can also perform theoperations on multiple rows simultaneously.Rule 8: Physical data independence:Changes to the physical storage structure must not require a change to an applicationbased on the structure.Rule 9: Logical data independence:Changes to the logical level (tables, columns, rows, and so on) must not require a change toan application based on the structure.Rule 11: Distribution independence:The distribution of portions of the database to various locations should be invisible to usersof the database.Rule 12: The non- subversion rule:If the system provides a low-level (record-at-a-time) interface, then that interface cannot beused to subvert the system, for example, bypassing a relational security or integrityconstraint.Note:- Any database management system which fulfills 6 or more than 6 rules can beconsidered as the RDBMS.Rules satisfied by Oracle RDBMSOracle RDBMS follows 11 out of 12 rules. One rule which is not followed is debatable. 1. View Updating Rule: It is because, according to Dr. E.F.Codd, every view should support full range of data manipulation, but in Oracle, it is not feasible for complex views based on multiple tables.ANKUR RAINA 09-IT-4505
  8. 8. 2. Systematic Treatment of Null value Null in Oracle is treated as absence of a value or unknown status ( in case of comparison of values ) and it does not have any systematic representation. In Oracle, no two null values are equal (as this will return a value which is treated as unknown by Oracle). If there is a systematic representation, then NULL value must be comparable.ANKUR RAINA 09-IT-4505
  9. 9. CHAPTER 3Oracle Database ArchitectureThe Oracle RDBMS consists of two main components:- 1. The Database or the Physical Structures 2. The Instance or the Memory StructuresControl Files:These files contain data about the database itself, called the metadata. These files arecritical to the database. Without them, one cannot open the data files to access the datawithin the database.Data Files:These files contain the data of the database.ANKUR RAINA 09-IT-4505
  10. 10. Online Redo Log Files:These files allow for instance recovery of the database. If the database were to crash andnot lose data files, the instance will be able to recover the database with the information inthese files.Tablespaces and Data Files:ANKUR RAINA 09-IT-4505
  11. 11. A database is divided into logical storage units called tablespaces, which can be used togroup related logical structures. Each database is logically divided into one or moretablespaces. One or more data files are explicitly created for each tablespace to physicallystore the data of all logical structures in a tablespace.Segments, Extents, and Blocks:Database objects such as tables and indexes are stored in tablespaces as segments. Eachsegment contains one or more extents. An extent consists of contiguous data blocks, whichmeans that each extent can exist only in one data file. Data blocks are the smallest units ofI/O in the database.When the database requests a set of data blocks from the operating system (OS), the OSmaps this to the actual OS block on the storage device. Because of this, one needs not to beaware of the physical address of any data in the database. This also means that a data filecan be striped and or mirrored on several disks.The size of the data block can be set at database creation time. The default size of 8K isadequate for more databases. If your database supports a data warehouse application thathas large tables and indexes, then a larger block may be beneficial. If your databasesupports a transactional application where reads and writes are very random, then a smallerblock size may be beneficial. The maximum block size is dependent on the OS. The minimumblock size is 2K and should rarely (if ever) be used.There are other files that are not officially part of the database, but are important to thesuccessful running of the database. These are:Parameter File:The parameter file is used to define how the instance will be configured when it starts up.ANKUR RAINA 09-IT-4505
  12. 12. Password File:This file allows users to connect remotely to the database and perform administrative tasks.Archive Log Files:These files contain an ongoing history of the redo generated by the instance. These filesallow for database recovery. By using these files and a backup of the database, it is possibleto recover a lost file.Oracle Instance ManagementAn Oracle Database server consists of an Oracle Database and an Oracle instance. An Oracleinstance consists of memory buffers known as the System Global Area (SGA) andbackground processes.The instance is idle (non-existent) until it is started. When the instance is started, aninitialization parameter file is read and the instance is configured accordingly.After the instance is started and the database is opened, users can access the database.ANKUR RAINA 09-IT-4505
  13. 13. Oracle Memory StructuresThe basic memory structures associated with an Oracle instance include:System Global Area (SGA):It is shared by all server and background processes.Program Global Area (PGA):It is private to each server and background process; there is one PGA for each process.The SGA is a shared memory area that contains data and control information for theinstance. The SGA consists of the following data structures:Database buffer cache: Caches blocks of data retrieved from the database.Redo log buffer: Caches redo information (used for instance recovery) until it can be writtento the physical redo log files stored on disk.Shared pool: Caches various constructs that can be shared among users.Large pool: Is an optional area used for buffering large I/O requests.Java pool: Is used for all session-specific Java code and data within the Java Virtual Machine(JVM).ANKUR RAINA 09-IT-4505
  14. 14. Stream pool: Is used by Oracle Streams.When we start the instance by using Enterprise Manager or SQL*Plus, the memory allocatedfor the SGA is displayed.A PGA is a memory region that contains data and control information for each serverprocess. A server process services a client’s requests. Each server process has its ownprivate PGA area that is created when the server process is started. Access to it is exclusiveto that is created when the server process is started. Access to it is exclusive to that serverprocess, and is read and written only by the oracle code acting on behalf of it.The amount of PGA memory used and its content depends on whether the instance isconfigured in shared mode. Generally, the PGA contains the following:Private SQL area: Contains data such as bind information and run-time memorystructures. Each session that issues a SQL statement has a private SQL area.Session memory: Is memory allocated to hold session variables and other informationrelated to the session.ANKUR RAINA 09-IT-4505
  15. 15. CHAPTER 4SQL StatementsSQL stand for Structured Query Language. SQL has become the de-facto standard languageused for creating and querying relational databases. The SQL statements can be categorizedas:-Types of SQL Statements:Data Manipulation Language:It constitutes those commands which are used to maintain & query a database, includingupdating, inserting, modifying and querying data.SELECTINSERTUPDATEDELETEMERGEData Definition Language:It constitutes those commands which are used to define a database including creating,altering and dropping tables and establishing constraints.CREATEALTERDROPRENAMETRUNCATECOMMENTData Control Language:It controls a database and deals with the administrative privileges.GRANTREVOKEANKUR RAINA 09-IT-4505
  16. 16. Transaction Control:A discrete unit of work that must be completely processed or not processed at all within acomputer system is called a transaction. The following commands control the transactions.COMMITROLLBACKSAVEPOINTCapabilities of SQL SELECT statements:The three basic capabilities of SELECT statements are:Projection: To choose the columns in a table that is returned by a query.Selection: To choose the rows in a table that is returned by a query. Various criteria can beused to restrict the rows that are retrieved.Joining: To bring together data that is stored in different tables by specifying the linkbetween them.Data Retrieval: Using SELECT Statement:SELECT identifies the columns to be displayed.FROM identifies the table containing those columns.If all columns are of data in a table are to be listed, an asterisk (*) can be used.ANKUR RAINA 09-IT-4505
  17. 17. Defining a NULL value:A null is a value that is unavailable, unassigned, unknown, or inapplicable. A null is not thesame as a zero. Columns of any data type can contain nulls. However, some constraints(NOT NULL and PRIMARY KEY) prevent nulls from being used in the column....Arithmetic expressions containing a null value evaluate to null....ANKUR RAINA 09-IT-4505
  18. 18. Defining a Column Alias:A column alias is used to rename a column heading. It is useful with calculations. It eitherfollows the column name or an optional AS keyword is used between the column name andalias. If the alias name is case sensitive, enclose it in double-quotation marks.Restricting Rows: Using WHERE clause:WHERE restricts the query to rows that meet a conditionCondition is composed of column names, expressions, constants, and a comparison operator.Character Strings and Dates:Character strings and date values are enclosed in single quotation marks. Character stringsare case sensitive, and date values are format sensitive. The default date format isDD-MON-RR.ANKUR RAINA 09-IT-4505
  19. 19. Comparison Conditions:ANKUR RAINA 09-IT-4505
  20. 20. Logical Conditions:ANKUR RAINA 09-IT-4505
  21. 21. Rules of PrecedenceSorting Data:Sort retrieved rows with the ORDER BY clause: 1. ASC: ascending order, default 2. DESC: descending order The ORDER BY clause comes last in the SELECT statement.ANKUR RAINA 09-IT-4505
  22. 22. Using Substitution Variables:Substitution variables are used to temporarily store values with a single-ampersand (&) anddouble-ampersand (&&) substitution. Substitution variables are used to supplement thefollowing: 1. WHERE clause 2. ORDER BY clause 3. Column expressions 4. Table names 5. Entire SELECT statements Use the double ampersand (&&) if you want to reuse the variable value without prompting the user each time.ANKUR RAINA 09-IT-4505
  23. 23. CHAPTER 5 Using Single Row Functions to Customize Output: Features: 1. Used to manipulate data items 2. Accept arguments and return one value 3. Act on each row that is returned 4. Return one result per row 5. May modify the data type 6. Can be nested 7. Accept arguments that can be a column or an expression General Functions:FUNCTION SYNTAX DESCRIPTION Converts a null value to actual NVL NVL(expr1,expr2) value. I f expr1 is not null, NVL2 NVL2 NVL2(expr1,expr2,expr3)returns expr2. If expr1 is null, NVL2 returns expr3. Compares two expressions NULLIF and returns null if they are NULLIF(expr1,expr2) equal; returns the first expression if they are not equal. Returns the first non-nullCOALESCE COALESCE(expr1,expr2,...,exprn) expression in the expression list.ANKUR RAINA 09-IT-4505
  25. 25. CASE Expression: It facilitates conditional inquiries by doing the work of an IF-THEN_ELSE statement.ANKUR RAINA 09-IT-4505
  26. 26. DECODE Function: It facilitates conditional inquiries by doing the work of a CASE expression or IF-THEN-ELSE statement.ANKUR RAINA 09-IT-4505
  27. 27. CHAPTER 6 Reporting Aggregated Data Using Group Functions: Group Functions: Group functions operate on sets of rows to give one result per row. Types of Group functions are: FUNCTION SYNTAX DESCRIPTION AVG AVG([DISTINCT|ALL]n) Average value of n, ignoring null values. COUNT COUNT({*|[DISTINCT|ALL]expr}) No. of rows where expr evaluates to something other than null(count all selected rows using * , including duplicates and rows with nulls) MAX MAX([DISTINCT|ALL]expr) Max value of expr ignoring null values MIN MIN([DISTINCT|ALL]expr) Min value of expr ignoring null values STDDEV STDDEV([DISTINCT|ALL]x) Standard deviation of n ignoring null values SUM SUM([DISTINCT|ALL]n) Sum values of n ignoring null values VARIANCE VARIANCE([DISTINCT|ALL]x) Variance of n ignoring null values COUNT (*) returns the number of rows in a table.ANKUR RAINA 09-IT-4505
  28. 28. COUNT (expr) returns the number of rows with non-null values for expr. COUNT (DISTINCT expr) returns the number of distinct non-null values of expr. Creating Groups of Data: GROUP BY Clause SyntaxANKUR RAINA 09-IT-4505
  29. 29. Using GROUP BY clause on multiple columns Restricting Group Results with HAVING clause: When you use the HAVING clause, the Oracle Server restricts groups as follows: 1. Rows are grouped 2. The group function is applied 3. Groups matching the HAVING clause are displayed.ANKUR RAINA 09-IT-4505
  30. 30. CHAPTER 7Displaying Data Using Multiple Tables Creating Natural Joins: The NATURAL JOIN clause is based on all columns in the two tables that have the same name. It selects rows from the two tables that have equal values in all matched columns. If the columns having the same names have different data types, an error is returned. If several columns have the same names but the data types do not match, natural join can be applied by using the USING clause to specify the columns that should be used for an equijoin. Use the USING clause to match only one column when more than one column matches. Table name or alias is not used in the referenced columns.ANKUR RAINA 09-IT-4505
  31. 31. Using Sub-Queries to Solve Queries: Sub-Query: A query within a query is known as a sub-query. A sub-query executes once before the main query. The result of sub-query is used by the main query.ANKUR RAINA 09-IT-4505
  32. 32. CHAPTER 8Manipulating Data: A Data Manipulation language (DML) statement is executed when you:  Add new rows to a table  Modify existing rows in a table  Remove existing rows from a table A transaction consists of a collection of DML statements that form a logical unit of work.INSERT Statement: Syntax: Implicit Method: omit the column from the column list. Explicit Method: Specify the NULL keyword in values clause.UPDATE Statement:UPDATE statement is used to modify the existing rows in a table. More than one row can beupdated at a time (if required).ANKUR RAINA 09-IT-4505
  33. 33. DELETE Statement:DELETE Statement is used to remove existing rows from a table.If one omits the WHERE clause, all the rows from the table will be deleted.TRUNCATE Statement:The TRUNCATE Statement removes all rows from a table, leaving the table empty and thetable structure intact. It is a Data Definition Language (DDL) statement rather than a DMLstatement; cannot easily be undone.ANKUR RAINA 09-IT-4505
  34. 34. ANKUR RAINA 09-IT-4505
  35. 35. CHAPTER 9Database Objects:CREATE Statement:ANKUR RAINA 09-IT-4505
  36. 36. CREATE TABLE using a Sub-Query:Dropping a Table:  All data and structure in the table are deleted.  Any pending transactions are committed.  All indexes are dropped.  All constraints are dropped.  You cannot roll back the DROP TABLE statement.ANKUR RAINA 09-IT-4505
  37. 37. Creating Other Schema Objects:Views:  To restrict data access.  To make complex queries easy.  To provide data independence.  To present different views of the same data.CREATE VIEW Syntax (simple view):CREATE VIEW (complex view):ANKUR RAINA 09-IT-4505
  38. 38. You cannot modify data in a view if it contains:  Group functions  A GROUP BY clause  The DISTINCT keyword  The pseudo column ROWNUM keyword  Columns defined by expressionsYou cannot add data in a view if following conditions along with conditions above prevail:  NOT NULL columns in the base tables that are not selected by the view.Sequences:A sequence  Can automatically generate unique numbers  Is a sharable object  Can be used to create a primary key value  Replaces application code  Speeds up the efficiency of accessing sequence values when cached in memoryIndexes:An index:  Is a schema object  Can be used by the Oracle server to speed up the retrieval of rows by using a pointer  Can reduce disk I/O by using a path access method to locate data quickly  Is independent of the table that it indexes  Is used and maintained automatically by the Oracle serverANKUR RAINA 09-IT-4505
  39. 39. Indexes are created in the following two ways:  Automatically: A unique index is created automatically when you define a PRIMARY KEY or UNIQUE constraint in a table definition.  Manually: Users can create non-unique indexes on columns to speed up access to the rows.Syntax:Synonyms:Simplify access to objects by creating a synonym (another name for an object). Withsynonyms, we can:  Create an easier reference to a table that is owned by another user  Shorten lengthy object namesANKUR RAINA 09-IT-4505
  40. 40. REFERENCES Web Resources  Codd_rules    Books:  Study material by Oracle University Press  Modern Database Management by Jeffrey A. Hoffer, Mary B. Prescott and Fred R. McFaddenANKUR RAINA 09-IT-4505