• Share
  • Email
  • Embed
  • Like
  • Save
  • Private Content
Intro to tsql   unit 8
 

Intro to tsql unit 8

on

  • 342 views

 

Statistics

Views

Total Views
342
Views on SlideShare
342
Embed Views
0

Actions

Likes
0
Downloads
19
Comments
0

0 Embeds 0

No embeds

Accessibility

Categories

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment
  • 1

Intro to tsql   unit 8 Intro to tsql unit 8 Document Transcript

  • Introduction To SQL Unit 8 Modern Business Technology Introduction To TSQL Unit 8 Developed by Michael Hotek
  • Defaults
    • A default can exist as a separate object
    • A default still follows the same rules as a default constraint, but gives the flexibility of reuse
    • create default default_name as
    • constant|expression
    • Once a default is created, it can be bound to multiple columns using sp_bindefault
  • Defaults
    • create default D_city as 'Chicago'
    • exec sp_bindefault D_city,authors.city
    • exec sp_bindefault D_city,employee.city
    • To unbind a default, use sp_unbindefault
    • To drop a default, use drop default
    • A default must be unbound from all columns before it can be dropped
  • Rule
    • A rule is the same as a check constraint, except it exists as an independent object
    • Just like a default object, this gives the flexibility to use the rule in many places
    • The name of the varibale used inside a rule is arbitrary and can not be directly accessed
    • create rule rule_name as
    • conditional_expression
    • create rule R_state as
    • @state in ('IL', 'MI', 'MA')
    • create rule R_salary as
    • @salary < 1000000
  • Rule
    • create rule R_state as @state in ('IL', 'MI', 'MA')
    • exec sp_bindrule R_state,authors.state
    • exec sp_bindrule R_state,employee.state
    • To unbind a rule, use sp_unbindrule
    • To drop a rule, use drop rule
    • A rule must be unbound from all columns before it can be dropped
    • Only one rule can be active on a column at a time
    • The last rule bound to a column is the one in effect
    • If the column also has a check constriant, then the only acceptable values are those that match both
  • User Datatypes
    • The true power of rules, defaults, and user datatypes comes when they are combined.
    • A rule and a default can be bound directly to a user datatype.
    • Since the datatype can be used in many columns, this allows you to enforce a rule or default from a single location with a single command
    • Any changes to the rule or default are automatically reflected in all columns where that datatype is used
    • A rule or default bound directly to a column override the rule or default bound to a column
  • Precedence
    • During an insert, a default is checked first and then any rule
    • During an update, the rule is checked first
    • A rule or default bound directly to a column overrides the rule or default bound to the user datatype
    • The last rule or default bound is the only one that is effective
    • If a rule is bound to a column that has a check constraint, the only allowed values are those that meet both the rule and constraint
  • Definitions
    • Just like every other object in the database, information concerning a rule or default can be obtained from the system procedure sp_helptext
    • sp_helptext object_name
  • Unique Index
    • Unique indexes are used to enforce uniqueness within a column or group of columns
    • A unique index is created in three cases:
      • Primary key constraint is defined
      • Unique constraint is defined
      • A unique index is explicitly created
    • When the index is created, the data is checked for uniqueness. If duplicates are present, the creation of the index fails
    • The index is then enforced on all subsequent inserts and updates
  • Implementing RI
    • Which method to choose?
  • Unit 8 Review
    • Defaults can be created as separate objects
    • sp_bindefault binds a default to a column or datatype
    • Rules can also be created as separate objects
    • sp_bindrule binds a rule to a column or datatype
    • Rules and defaults promote reusablity
    • They can be combined with user datatypes for increased power and flexibility
    • The last rule or default bound to a datatype takes effect
    • A rule or default bound directly to a column overrides a rule or default bound to the column's datatype
    • A unique index is used to enforce uniqueness within a column or group of columns
  • Unit 8 Exercises
    • Time allotted for exercises is 30 minutes