CIS282 Midterm review


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CIS282 Midterm review

  1. 1. CIS282
  2. 2. Database Server Operates as a separate “process” Need to communicate with the server using a separate application  Connection required to transmit request and response  Management Studio and SQL Server are different programs
  3. 3. Managing SQL Server Management Studio gives access to most functions/operations Query window provides method to write/execute T- SQL statements  “T” = transact SQL Service Manager provides way to start/stop Server
  4. 4. SQL Server Databases Two files are maintained  Data file (.mdf)  Transaction Log file (.ldf) Files can be spread over multiple machines  Always need a primary file group
  5. 5. Database Contents Tables  User tables hold data  System tables hold data about the database Stored Procedures, User Defined Functions Views Indexes
  6. 6. Default Databases Master: Logins/User roles; system configuration; names/locations of databases; SQL Server startup Tempdb: Lasts duration of SQL Server session; temporary holding space Model: Sets characteristics of new databases MSDB: Holds information about jobs SQL Server Agent runs
  7. 7. Security Windows Authentication: Windows network logins used Mixed-mode: Windows OR SQL Server logins used Login: To access server User: To access a database Network security trumps all….
  8. 8. Roles Server – administrative functions  Task based:  Backup  Create database  Roles are fixed Database/Application – groups of users with common activities  Read/write all data  Read/write select data  Read data only
  9. 9. Normalization Process for reducing duplicate and redundant data 1st Normal Form: eliminate repeating groups 2nd Normal Form: each column in a table depends on the primary key  can’t get information with only part of the key 3rd Normal Form: A column cannot be dependent on another column that isn’t the primary key
  10. 10. Relationships Types  One-to-one  One-to-many  Many-to-many Requires a primary key on the ‘one’ side, foreign key on the ‘many’ side Referential Integrity defines how values work across tables
  11. 11. Table Definition Fields need a name and datatype  SQL Server datatypes are different from Access and procedural programming language datatypes Fieldnames can include spaces – but poor practice Identity – create unique number for each row
  12. 12. Constraints Allow Null – value not required to add record Check Constraints – test field or row values Default value – if no data is entered into a field Unique – values must be different for each row
  13. 13. Database Diagrams Illustrate database design Add, modify tables, indexes, relationships Can control view, table details
  14. 14. Indexes Help to select and find records Serve as a “cross-reference” Can be based on one or more fields
  15. 15. Good Index Characteristics Low maintenance columns Includes columns used frequently in Where or Order By clauses Don’t have to go out to table for data Help search for ranges of records
  16. 16. Action Queries Insert: insert into tablename(fieldlist) values(valuelist) Update: update tablename set field1=value1, field2=value2 Delete: delete from tablename [where condition]
  17. 17. Select Statement Can use an alias for fields and/or tables Select fields From table  Join table On field=field  Inner – both tables have records with matching values  Outer – all records from one table and any matches found in second table
  18. 18. Where Conditions to determine records returned Multiple conditions require And … Or Can use where clause to implement join between tables Sub-queries allow tables to be limited by values in a second table without using a join
  19. 19. Views Pre-defined select statement Used like a virtual tableSELECT * FROM v_CurrentEmployees
  20. 20. View Performance By default views run just as a query processed from command line  Adds second step to execution:  select from view  execute view itself Can add an index to speed execution  Specific requirements when creating an index on a view