Elegant and Efficient Database Design
- 1. Elegant & Efficient Database Design Tim Allen Becky Sweger
- 4. Jana
- 5. John-David
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- 8. Jinger
- 9. Josiah
- 10. Joy-Anna
- 11. Jedidiah
- 12. Jeremiah
- 13. Jason
- 14. James
- 15. Justin
- 16. Jackson
- 17. Johannah
- 18. Jennifer Naming ConventionsPick one and enforce it: camelCase, PascalCase, under_scoresWhy?Cleaner codeLogical joinsSanity of future developers and future youExplicitly name constraintsAvoid keywords as column namesWRDS Fail: group, client, school, subscriber, and institution are all used for the same data entity
- 19. DB Normalization
- 20. DB NormalizationThe key, the whole key, and nothing but the key. So help me Codd.
- 22. Why normalize?Avoid data duplicationLet end users make their own changesAvoid data anomaliesThird-party tools rely on normalized data
- 23. IndexingFind a book in Van Pelt without a card catalog…
- 25. Indexing: Clustered B-TreeIndexes in SQL Server are organized as B-treesmember name clustered index (image from Clustered Indexes vs. Nonclustered Indexes in SQL Server:http://tr.im/AeU5)
- 26. Indexing: Non-Clustered B-Treemember id non-clustered index (image from Clustered Indexes vs. Nonclustered Indexes in SQL Server:http://tr.im/AeU5)
- 27. Indexing: Other TypesUniqueFull-textIncluded columnsIndexed viewsXMLFiltered (new for 2008)Spatial (new for 2008)http://msdn.microsoft.com/en-us/library/ms175049.aspx
- 28. Indexing: Primary KeysPrimary key = unique index (clustered or non-clustered)
- 29. Indexing considerations: tablesClustered index on every tablemember name non-clustered index (image from Clustered Indexes vs. Nonclustered Indexes in SQL Server:http://tr.im/AeU5)
- 30. Indexing considerations: tablesInteger primary key on every table/* take checkpoint, clear buffers & cache */SELECT s.term, s.section_id, COUNT(penn_id)FROM flat_section s JOIN flat_enrollment eON s.section_id = e.section_idAND s.term = e.termGROUP BY s.term, s.section_id
- 33. Indexing considerations: columnsColumns you join on: indexed integers are your friend!How are the columns used in queries?Cardinality: 1:1, 1:many, many:manyData typeIndexing multiple columns: moderationGoal 1: performance!Goal 2: smallest index file possible.
- 35. Indexing Considerations: Yes! No!TINY: 8 bits (0 – 255): 01010101SMALL INTEGER: 16 bits (0 – 65536): 0101010101010101INTEGER: 32 bits (0 – 16777215): 01010101010101010101010101010101VARCHAR ‘philadelphia’: 104 bits, at least (encoding UTF-8): 01010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101Consider joining 4 tables on ‘philadelphia’: 4 initial lookups on indexes, 8 times as bulky and less cacheable as a small integer.Index on VARCHARs only when neededKeeps index files smaller and less chance of fragmentation; fragmented index files make Matt Frew’s life hellish (no, that is NOT a positive!)Consider purpose: don’t index for a one time script or report
- 37. Indexing Example: WRDS QueriesLarge table: millions of rowsA record for each WRDS queryVARCHAR columns that should be INTEGERSReport requests for subscribers asking number of queries for a date range group by library and fileBefore indexing, full table scan: 30 secs per queryIndex added: subscriber, query date, library, fileAfter indexing, without table scan: 0.02 secs per query
- 38. Indexing Tools: SSMSFrom the Query menu:SET STATISTICS TIME, SET STATISTICS IOInclude Actual Execution Plan
- 39. Indexing Tools: DMVDynamic Management Views & Functions: http://msdn.microsoft.com/en-us/magazine/cc135978.aspx
- 40. Indexing Tools: Tuning AdvisorAnalyzes workloads
- 41. Best Practices: Blame!Blame the SQL Admins!
- 42. Best Practices: Data TypesDon’t skimp on column length: Yes/No? Maybe. Open/Closed? Under construction. Black/White? Grey.Know required level of precision, and leave yourself room to grow.Accuracy to the day, minute, millisecond?
- 43. Best Practices: DeletionLogical deletes vs. physical deletes
- 44. Best Practices: work the DBForeign KeysUnique indexesCheck constraintsDefault constraintsTriggersimage courtesy of My New Filing Technique is Unstoppable by David Rees: http://www.mnftiu.cc/2002/11/26/filing-009/ (nsfw)
- 45. Best Practices: master tables
- 46. Best Practices: Crunch Time!“Temporary” projectsBalance between today’s pragmatism and tomorrow’s painCode review sooner
- 47. Best Practices: ExperimentExperiment in SQL Server Management Studio to improve your times and execution plans
- 48. Be Opinionated!Solicit feedback on database design before coding starts, not after.Ask for opinions, and share your opinions!More eyes = better database designMore ideas = better database designAnyone have any tips… or questions?
- 49. ResourcesSQL Server Books Online http://msdn.microsoft.com/en-us/library/ms130214.aspxSQL Server 2008 Query Performance Turning Distilled by Grant Fritchey and Sajal DamComparing Tables Organized with Clustered Indexes versus Heapshttp://technet.microsoft.com/en-us/library/cc917672.aspxMS Index Design Guidelineshttp://msdn.microsoft.com/en-us/library/ms191195.aspxClustered Indexes vs. Nonclustered Indexes in SQL Serverhttp://digcode.com/default.aspx?page=ed51cde3-d979-4daf-afae-fa6192562ea9&article=443e9774-7d26-422d-a2f1-dbcafbb1e1fc&pc=5SQL Server Execution Plans (free e-book, registration required)http://www.sqlservercentral.com/articles/books/65831/Uncover Hidden Data to Optimize Application Performancehttp://msdn.microsoft.com/en-us/magazine/cc135978.aspxMy New Filing Technique is Unstoppable (NSFW)http://www.mnftiu.cc/2002/11/26/filing-001/SQL in the Wildhttp://sqlinthewild.co.za/Journey to SQL Authority With Pinal Davehttp://blog.sqlauthority.com/