Index and types of Index used in Oracle.pptx
- 1. Index Management Database Administration and Management
- 2. Need of Index When we run query (Select marks from student where marks <33); OR When we run query (Select sale from employee where salary <5000); ο΅ Frequently verifying conditions ο΅ Frequently assessing ο΅ Assessing multiple records Index ο΅ Index maintains column data in ascending order ο΅ It also maintain addresses Why we use Index ο΅ Decrease no. of verification ο΅ Save time ο΅ Better performance
- 3. Example Roll_No Name Marks Address Roll_No Marks 1 Ali 45 BWP 5 22 2 Usama 87 LHR 6 30 3 Usman 48 BWP 1 45 4 Ahmed 64 BWP 3 48 5 Amir 22 BWP 4 64 6 Umer 30 LHR 2 87
- 4. Types of Index ο΅ Simple Index ο΅ Composite Index ο΅ Unique Index ο΅ Reversing Index ο΅ Function based Index ο΅ Bitmap Index Simple Index ο΅ Index create on single column. e.g., sale from employee table ,marks from student table, etc. Query ο΅ Create INDEX IDX_SALARY on employee(sale); ο΅ Searching in index, not table
- 5. Composite Index ο΅ Index creates on multiple columns on any table. Query ο΅ Create INDEX idx_s.no_rollNo on students(s.no, rollNo); Unique Index ο΅ Index creates on columns -----ο no duplication Query ο΅ Create UNIQUE INDEX idx_mobileNo on customers_dtls(mobile); Reversing Index ο΅ Want to search data frequently looking for highest value. ο΅ Normally List values-------ο beginning, Highest value---------ο ending ο΅ Its searching is fast because its work in reversing order. ο΅ Based on Binary tree.------ο right to left in b.tree. ο΅ Create INDEX idx_sales_amt on sales(sales_amt) REVERSE;
- 6. Function based index ο΅ Work on function based. ο΅ Suppose I have a table of employee, and have a column of emp_id,salary,commission Query ο΅ Select e_id,sal(0.100*sal) from emp ο΅ Create Index idx_sal on emp(sal(0.100*sal))init cap(ename); Bitmap index ο΅ Bits ---------ο 0,1 ο΅ Less number of values in columns ο΅ E.g., ο΅ status--ο active/inactive, ο΅ Gender--ο male/female Query ο΅ Create bitmap Index id_gender on customer(gender); Note: ο΅ All index created based on the binary tree index.