Chapter 2 Basic SQL SELECT Statements

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Chapter 2Basic SQL SELECT Statements
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Relational Database Management System (RDBMS)

• An RDBMS is the software program used to create
  the database and it allows you to enter,
  manipulate, and retrieve data

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Object Relational Database Management System
(ORDBMS)

• Same as an RDBMS except it can be used to
  reference objects such as maps and object fields

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SELECT Statement Syntax

• SELECT statements are used to retrieve data from
  the database
• Syntax gives the basic structure, or rules, for a
  command

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SELECT Statement Syntax

• Optional clauses and keywords are shown in
  brackets

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SELECT Statement Syntax

• SELECT and FROM clauses are required
• SELECT clause identifies column(s)
• FROM clause identifies table(s)
• Each clause begins with a keyword

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Selecting All Data in a Table

• Substitute an asterisk for the column names in a
  SELECT clause

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Selecting One Column from a Table

• Enter column name in SELECT clause

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Selecting Multiple Columns from a Table

• Separate column names with a comma

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Operations Within the SELECT Statement

• Column alias can be used for column headings
• Perform arithmetic operations
• Suppress duplicates
• Concatenate data

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Column Alias

• List after column heading
• AS keyword is optional
• Enclose in double quotation marks
• If it contains blank space(s)
• If it contains special symbol(s)
• To retain case

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Column Alias Example
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Precedence of Arithmetic Operations

• Executed left to right
• Multiplication and division are solved first
• Addition and subtraction are solved last
• Override order with parentheses

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Example Arithmetic Operation with Column Alias
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Suppressing Duplicates

• Enter DISTINCT or UNIQUE after SELECT keyword

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Concatenation

• Can combine data with string literal
• Use concatenation operator,
• Allows use of column alias

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Concatenation Example