Database Refactoring Sreeni Ananthakrishna 2006 Nov
1. Database Refactoring An introduction to Refactoring Databases & Evolutionary Database Design (Amber and Sadalage)
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4. A simple example… Customer accesses balance Customer SynchronizeAccountBalance {event = on update |on delete|on insert, drop date = <date> } balance SynchronizeCustomerBalance {event = on update |on delete|on insert, drop date = <date> } {drop date = <date>} App A App B maintainbalance() maintainbalance() customerId <<PK>> name Account accountId <<PK>> customerId <<FK>>
16. Introduce Surrogate Key (contd.) contains balance PopulateOrderId {event = on insert drop date = <date> } orderId <<FK>> <<surrogate>> orderId <<PK>> <<surrogate>> {drop date = <date>} Order customerNumber <<PK>> <<FK>> <<Natural>> storeId <<PK>> <<Natural>> OrderItem customerNumber <<PK>> <<FK>> <<Natural>> storeId <<PK>> <<Natural>> orderItemNumber <<PK>>
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19. Add Lookup Table (contd.) Address Street <<FK>> 1. Identify the column 4. Introduce FK constraint 3. Populate Data 2. Create Lookup Table State PostCode State State <<PK>> Name
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22. Introduce Cascading Delete (contd.) Policy PolicyId <<PK>> Claim ClaimId <<PK>> 1. Identify the column 2. Choose cascading mechanism (triggers or using cascade clause during constraint creation) PolicyId <<FK>> DeleteClaim {event = on delete}
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25. Introduce Index (contd.) Customer CustomerId <<PK>> TFN <<index>> 1. Determine type of index – unique vs non-unique 3. Add a new index TFN <<AK>> Name 4. Add more disk space for index maintenance 2. Eliminate duplicate rows when using unique index
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