DATABASE (2ND YEAR 3RD TERM)

• INTRODUCTION TO COMPUTING
• Course Code: CCINCOM/L
• Joseph Marvin R. Imperial
• NU College of Computing and Information Technologies
• SELECT QUERY
• Lord Edgardian J. Tavu, MSCS
• CS Program Chair
• ADVANCED DATABASE SYSTEMS
• Course Code: CTADVDBL
• Department of Computer Science
• College of Computing and Information Technologies (CCIT)
• National University
• SELECT query


  Specifies the columns to be retrieved as a column list
• Syntax for a basic SELECT query


  1. SELECT columnlist

  2. FROM tablelist
• columnlist


  One or more attributes, separated by commas
• Wildcard character (*)


  Symbol that can be used as a general substitute for other characters or commands, meaning "all columns"
• SQL Data Manipulation Commands
• SQL Data Manipulation Commands


  • SELECT
  • FROM
  • WHERE
  • GROUP BY
  • HAVING
  • ORDER BY
• SELECT


  Selects attributes from rows in one or more tables or views
• FROM


  Specifies the tables from which data should be retrieved
• WHERE


  Restricts the selection of rows based on a conditional expression
• GROUP BY


  Groups the selected rows based on one or more attributes
• HAVING


  Restricts the selection of grouped rows based on a condition
• ORDER BY


  Orders the selected rows based on one or more attributes
• Column alias


  New name specified for a column, used as a label or heading in the query output
• Computed column


  Derived attribute, may or may not be stored in the database
• Arithmetic operators


  +, -, *, /, ^
• Rules of precedence


  • Perform operations within parentheses
  • Perform power operations
  • Perform multiplications and divisions
  • Perform additions and subtractions
• Comparison operators


  • =, <, >, <=, >=, <>, !=
• Logical operators


  • AND, OR, NOT
• Aggregate functions


  • COUNT, MIN, MAX, SUM, AVG
• Special operators


  • BETWEEN, IN, LIKE, IS NULL, EXISTS, DISTINCT
• DISTINCT


  Limits values to unique values
• Nulls can be problematic when writing SQL code as different operators and functions treat nulls differently