Intro to tsql unit 6

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Transcript

  • 1. Introduction To SQL Unit 6 Modern Business Technology Introduction To TSQL Unit 6 Developed by Michael Hotek
  • 2. Temporary Tables
    • Temp tables are used to hold intermediate result sets for further processing
    • These are used when you need to perform a process that can not be done in a single SQL statement
    • They come in two different types
    • local
      • accessible only to that connection
      • preceeded by a # ex: #authors
      • dropped when the session disconnects
    • global
      • accessible to all connections
      • must be explicitly dropped
      • preceeded by ## ex: ##authors
    • Names can only be 13 characters long
  • 3.
    • Temp tables can be a powerful addition to your code
    • They should be minimized at all costs
    • Many people overuse temp tables
      • Poor database design
      • Lack of SQL knowledge
      • Lazy
    • Temp tables can impose a significant drain on system resources
    Temporary Tables
  • 4. Select Into
    • Select into can be used to create a new table based upon a select statement
    • Creates the table to match the structure of the select list
    • Adds any data from the select
    • The database option select into/bulkcopy needs to be turned on
    • SELECT [ALL | DISTINCT] select_list [ INTO [ new_table_name ]] [FROM { table_name | view_name }[ ( optimizer_hints ) ] [[ , { table_name2 | view_name2 }[ ( optimizer_hints ) ] [... , { table_name16 | view_name16 }[ ( optimizer_hints ) ]]] [WHERE clause] [GROUP BY clause] [HAVING clause] [ORDER BY clause]
  • 5. Select Into
    • To create an empty table, include a where clause that will always be false
    • select * into temptitles from titles
    • where 1 = 2
    • It is highly recommended to do this and then insert the data into the table in a separate operation
    • Rules, defaults, constraints, indexes, triggers, etc. are not associated with the new table
  • 6. Views
    • Views are nothing more than a name for a select statement that is stored in the database
      • Behave exactly like a table
      • Do not store any data
      • May include more than one table
      • Simplify and/or customize data
      • Provides independence from the database schema
      • Provides security
    • The main factor in using security should usually be security
  • 7. Views
    • CREATE VIEW [ owner . ] view_name [ ( column_name [ , column_name ]... ) ] [WITH ENCRYPTION] AS select_statement [WITH CHECK OPTION]
    • Always explicitly specify the columns that will be included
    • With encryption means that the definition of the view is encrypted when it is stored
  • 8. With Check Option
    • The with check option restricts the data that can be inserted and updated through a view
    • Leaving this out, allows inserts and updates to the underlying data that might not show up in the view due to the where clause
    • When this is included, the insert and update must conform to the where clause of the view
  • 9. Restrictions
    • Another view can be included in the definition of a view, but only 16 tables/views can be emcompassed
    • Clauses not allowed
      • order by
      • compute/compute by
      • select into
    • Updates can be performed through a view as long as only one table at a time is updated
    • Updates can not be performed is a distinct, group by, or aggregate is included in the view
  • 10. Unit 6 Review
    • Temporary tables can be created to hold intermediate result sets
    • Temp tables are either local or global
    • Select into can be used to create either a permanent or temporary table
    • Views can be defined to provide alternate access to data
    • Views primary consideration should be security
  • 11. Unit 6 Exercises
    • Time allotted for exercises is 30 minutes