1. Softsmith Infotech Oracle Table of contents What is a database? Fundamentals of database Table management Inserting data Updating data Deleting data Query management –Simple queries –Aggregate functions –String manipulation –Date manipulation –Sub queries –Equi join –Outer join –Self join –Union, intersection, minus View management Sequence Management Index Management Constraints Management Triggers Stored procedures Exceptions Sequences Constraints DBA features

2. Softsmith Infotech Fundamentals of database Applications are used by end users and they enter a group of raw data This data is later collated and used by management to arrive at meaningful information Before we first understand the technical aspects of database, we must understand the business data clearly Rule 1: In any application, first identify raw data Rule 2: Group related data and associate data type and size (summary and detail) Rule 3: Create a set of samples for each of these groups for better clarity Rule 4: Identify unique and non-unique data Rule 5: Identify the relationship between the data

3. Softsmith Infotech Raw Data and Grouping Let us take railways reservation as the application The raw data could be –Passenger name –Age –Date of journey –Train name –From station –To Station –PNR number –Route codes –Stations covered in the route The data groups would be Train related data – train number, train name, route in which it is running Station related data – station code, station name, station RMS Pincode, station type (junction, station etc) Ticket related data – PNR Number, passenger name, date of journey, set or berth, age, from station, to station, train code etc

4. Softsmith Infotech Unique and non-unique data Unique data means a data that does not repeat itself Station code is unique across country Train code is unique across country PNR number is unique across country Coach number is unique within a train, but not unique across system Seat number is unique within a coach and train Passenger name is not unique Ticket price is not unique

5. Softsmith Infotech Relationship between data One PNR number is associated with one train code One PNR number is associated with one or more passenger names One train code is associated with one or more stations One train code is associated with one route code All relationships will fall under one-to-one, one- to-many, many-to-one Many-to-many is a combinations of the above We need to identify the relationships between the data to understand clearly the dependency between data

6. Softsmith Infotech Components of database A physical database installation in a machine has the following logical entities –Database (group of tables) –Tables (that contain data) –Views –Index files –Triggers –Sequences –Stored procedures (packages, functions, procedures) –Users to access the tables

7. Softsmith Infotech Table Management Create, alter and drop are the operations on a table To create a table, we need to supply the table name, column names and attributes, for each column whether it is a null or not null column, what is the default value for that column, whether the column is primary key or not CREATE TABLE is the command to be used When we want to add a column to a table or to change the attributes of a column in a table, we use ALTER TABLE command We cannot remove a column from a table If we want to remove the table from the database, we need to use DROP TABLE command When a table is dropped, the data is also lost Dual is a default built-in table to do any on the fly calculations The usual column data types will be number, varchar2, char, date

8. Softsmith Infotech Inserting Data INSERT operation into a table requires data to be entered We can insert all column values or selective column values When insert is successful, we will get a success message When we try to enter a duplicate value into a table, we will get duplicate constraint violation message During insert, if we do not supply a value, the default value for a column is used to fill up that column We can insert data only to one table at a time

9. Softsmith Infotech Update Operation When we want to modify data in a table, we can use UPDATE command We can update only one table at a time When we update we need to use the SET clause to set the values for a particular column During update also, if try to update a record, such that it results in duplicate record, we will get a unique constraint violation message If we use update command without WHERE clause, it will update all the records It is not recommended to update, without giving a where clause Examples –Update employee set salary = 1000 –Update employee set salary = 2000 where designation = ‘SALESMANAGER’

10. Softsmith Infotech Delete Operation When we want to remove data in a table, we can use DELETE command We can delete only one table at a time We cannot delete a particular column; it is always one row or multiple rows If we use delete command without WHERE clause, it will delete all the records It is not recommended to delete, without giving a where clause Example –delete from employee –Delete from employee where designation = ‘HRMANAGER’

11. Softsmith Infotech SELECT Queries When we want to retrieve data from a table, we use SELECT clause Most of the times, testers use SELECT queries only SELECT has a lot of variations and clauses. Hence SELECT is a must for all testers SELECT queries can handle date and string manipulation commands as well SELECT helps to filter, search and sort data SELECT helps to find out relationships in data

12. Softsmith Infotech Simple query SELECT * from TRAINS –this will get all columns in the table SELECT TRAIN_CODE, TRAIN_NAME from TRAINS –this will return only 2 columns from the table SELECT TRAIN_NAME from TRAINS WHERE number_of_coaches > 15 –This is a simple filter SELECT TRAIN_NAME from TRAINS WHERE number_of_coaches > 15 AND TRAIN_CODE < 100 –This is a complex filter

13. Softsmith Infotech Aggregate functions Aggregate functions work on the whole set of records SELECT max(salary) from EMPLOYEE –this will get the maximum salary data from the table SELECT min(salary) from EMPLOYEE –this will get the minimum salary data from the table SELECT avg(salary) from EMPLOYEE –this will get the average salary data from the table SELECT count(*) from EMPLOYEE –this will get the number of records in the table SELECT sum(salary) from EMPLOYEE –this will get the sum of all salary data from the table

14. Softsmith Infotech String/Numeric/Date Manipulation Functions Lower – this will convert to lower case Upper – this will convert to upper case Substr – this will return a portion of the string Soundex – will look for sounding matches Floor – will show the lower side value Ceil – will show the upper side value Round – will round off the number to the nearest value Sysdate – will show the current date Current_timestamp – will show the current timestamp To_date and to_char – to manipulate date formats

15. Softsmith Infotech Operators We can use arithmetic operators like +, -, *, / Logical operators are AND, OR, NOT Open and close brackets are used to group items % is used along with LIKE operator Where firstname LIKE ‘%raj%’ will search for raj anywhere in firstname column Distinct is an operator on a column to fetch distinct values present in all rows IN operator is used to provide a set of values in the WHERE clause BETWEEN operator is used to provide a range of values in the WHERE clause

16. Softsmith Infotech SubQuery Sub query is query within a query This is used to ensure that the WHERE condition is further getting values from another query Select employee_name, salary from employee where designation = (select designation from positionmaster where positioncategory like ‘%MANAGER%’) The innermost select is executed first and then the outer select is executed In sub queries, if we use = in where condition, the subquery must return only one value In sub queries, if we use IN clause in where condition, the subquery can return more than one values

17. Softsmith Infotech JOINs Joins are nothing but a cross product of one or more tables Inner join is used to get records that match a condition in all tables In joins we use alias to denote table names Outer join is used to get records from more than one tables, irrespective of the condition match in left or right table Example –SELECT a.empname, b.projectname from employees a, projects b where a.employeecode = b.employeecode and b.projectstatus = ‘Active’ To create outer join we use + sign to the left table or right table

18. Softsmith Infotech Union, Intersect, Minus Union is used to combine many SELECT queries. The result will be all records fetched by all queries. If 2 records match in 2 different queries, it is printed once in the result Intersect is used to combine many SELECT queries. The result will be the common records between the 2 select queries Minus is used to find out the difference between 2 SELECT queries In all these cases, the columns selected must be the same in all select statements We can use all these to find the referential integrity of the database

19. Softsmith Infotech Views A view is a virtual table A view is used to simplify a complex select statement A view can bring multiple data from many tables For all query purposes, a view is treated as a table Create View SalesPeople As Select employeename from employees where designation like ‘%SALES%’ When we create views, our job to write complex queries get reduced

20. Softsmith Infotech Index Files, Transactions Index files are pointers to the exact location of a record on the disk These help us to search faster. Hence a query executes faster If we do not have index on a column, and we search based on that column, it becomes sequential. The performance will be poor Index can be unique or non-unique By using index files, search works as binary search When we do insert or update or delete, we can make that permanent by issuing a COMMIT statement If we want to ignore the previous insert, update, delete statements, we use ROLLBACK statement

21. Softsmith Infotech Triggers Trigger is an automatic event that happens based on insert or update or delete We cannot pass parameters to triggers A trigger can happen before or after the operation Create or replace trigger is used to get the trigger in database :NEW.column or :OLD.column is used to retrieve internal values when the triggers are fired Drop trigger is used to remove the trigger To test a trigger, first do the required insert or delete or update operation on the primary table Do a select query on the other tables on which the trigger operated

22. Softsmith Infotech Stored Procedures These are executable code written in PLSQL These reside inside oracle We can write loops, conditions etc including exception handling This comes in 2 parts – package header and package body The package header contains procedures and function definitions The package body contains actual executable code of functions and procedures Procedures and functions take parameters They must be explicitly executed and they are not automatic Before executing procedures, set serveroutput on Functions must return a value to the left hand side Usually functions are used when there is only one return value or there is a true/false returns Inside stored procedures, people write any database queries as required by application logic To execute, from the prompt, give –exec packagename.procedurename(paramaters)

23. Softsmith Infotech Exceptions Exceptions must be handled inside stored procedures or triggers This will ensure that the code does not crash When Others is the generic exception SQLCODE and SQLERRM will hold the error number and error text Usually no_data_found and dup_val_on_index are checked in most of the places

24. Softsmith Infotech Cursors When a stored procedure needs to retrieve only one record, we use into clause in the select statement When the procedure needs to process a record set, we use cursor Declare the cursor and provide the select statement Use OPEN, FETCH and CLOSE commands to access the cursor Cursorname%notfound will be set to true if there are no more records to fetch Cursorname%count will provide the number of records in the cursor

25. Softsmith Infotech Sequences Sequences are used to generate auto increment values Use Create sequence command and provide minimum, maximum, start and increment values Sequcen.nextval will provide the next sequence number This can be used in any insert statements subsequently

26. Softsmith Infotech Constraints Not Null is a constraint while creating a table Primary Key is a constraint Foreign Key is a constraint Check is a constraint to ensure that a column has only specified values Unique index is also a constraing

27. Softsmith Infotech DBA Features This list gives only the features and not detailed information –Creating database –Creating users –Providing access rights to users across tables –Backup and restore –Crash recovery –Replication –Loading of bulk data –Partitioning of data across disks