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Refining the Server Model

Refining the Server Model. Adding New Tables. New Table. New View. New Snapshot. New Cluster. New Column. New Man FK. New Opt FK. Add a Foreign Key. Create Index for FK. DDT Automatically Creates Index for FK. Other Columns to Index. Key columns Columns used frequently in queries

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Refining the Server Model

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  1. Refining the Server Model

  2. Adding New Tables New Table New View New Snapshot New Cluster New Column New Man FK New Opt FK

  3. Add a Foreign Key

  4. Create Index for FK DDT Automatically Creates Index for FK

  5. Other Columns to Index • Key columns • Columns used frequently in queries • Columns with many distinct values • Guidelines: • Start with the least number of indexes • Add indexes as the data grows • Check both query and DML perfomance

  6. NAME JOB HIREDATE Choosing the Number of Indexes • More indexes = slower insert and delete • Concatenated indexes can help Queries: NAME = 'SMITH'; JOB LIKE 'SALES%' AND NAME = 'SMITH'; JOB = 'CLERK'AND NAME = 'SMITH'AND HIREDATE > '1-JUN-98'; HIREDATE = '31-DEC-98'; Indexes: NAME JOB HIREDATE

  7. 3 2 1 Oracle Sequence • Database object: • Generates unique numbers • Minimizes contention • Gaps in sequence

  8. Adding Surrogate Key Create a Sequence Create Key Assign to Column

  9. DDT Surrogate Keys • Automatically creates key • Automatically creates sequence • Automatically assigns sequence to key column

  10. Oracle Sequences • Efficient • Have Gaps • Rolled back transactions do not return used sequence numbers

  11. CC_DOMAIN CC_NEXT VALUE CC_INCREMENT CC_DOMAIN CC_NEXT VALUE CC_INCREMENT 1 1 1 1 EMP_SEQ1 EMP_SEQ1 EMP_SEQ1 EMP_SEQ1 2018 2017 Eliminating the Gaps CG_CODE_CONTROLS EMPLOYEES IDENTIFIER LAST_NAME 2016 SMITH Newrow 2017 HAMBURG

  12. Creating a Code Control Sequence Sequence Definitions ? Create Sequence: Name 1 2 3 Name of the sequence Purpose of the sequence Sequence type ORACLE sequence Code control sequence

  13. Sequence Within Parent • Generate a value within the context of the parent record RENTAL_ITEMS RENTALS RE_ID LINE_NO RE_ID 1 1 1 2 2 1 2 1 2 2

  14. Column Properties Derivation Autogen Type … Seq in Parent Creating a Sequence Within a Parent Set AutoGen Type to Seq in Parent

  15. Choosing a Method • Oracle sequence: • Sequential values with gaps • Recommended • Code control sequence: • Databases other than Oracle • Sequential values without gaps • Contention can be tolerated • Sequence within a parent: • Minimal number of detail records

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