SQL

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SQL

• FIS 1311
• Nov. 28, 2005

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Structured Query Language

• ANSI/ISO standard used with relational databases
• Is a very simple but powerful computer language
• Tells the computer/database what to do
• Sequences of linked commands can perform complex
  tasks
• Represents a formalized language that utilizes
  datatypes, boolean operators

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Structured Query Language, Cont

• What can it do?
• Define, very precisely, the retrieval of
  information from relational databases
• Insert and update data in these databases
• Create and define tables
• Perform elementary analysis/manipulation of
  retrieved results
• Viewing/formatting data in different ways

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Anatomy of a select statment

• SELECT describe fields you want to see/retrieve
• FROM table(s) where the fields are found
• WHERE describe one or more conditions that will
  restrict the number of fields retrieved
• Display information ORDER BY, Remove duplicates

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WHERE - Conditions

• Equal
• ltgt or !Not Equal
• lt Less Than
• gt Greater Than
• lt Less Than or Equal To
• gt Greater Than or Equal To

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WHERE - Conditions, cont

• IN Allows the user to supply a list of values as
  conditions in a query. (Could be either numeric
  or textual, but are generally textual)
• BETWEEN Allows the user to select a range of
  values as a query condition. (Tends to be
  numeric.)
• LIKE Used with the sign, which can stand in for
  any character or set of characters

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Dataypes

• Individual fields can/will have different
  datatypes.
• These are important in SQL syntax in conditional,
  when clauses
• If its text, use single quotes WHEN
  last_namefriesen like norm
• If its numeric, dont use quotes WHEN ID gt 5
• Numbers or combinations of numbers and other
  characters can be used and ordered, etc. as text
  datatypes

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Practice, Practice

• learningspaces.org/1311/sql/select-1.cfm
• Use this, and see what happens!