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MySQL Tutorial - Using CASE Expression

By: FYIcenter.com

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How To Use CASE Expression?

There are 2 ways to use the CASE expression. The first way is to return one of the predefined values based on the comparison of a given value to a list of target values. The second way is to return one of the predefined values based on a list of conditions. Here is the syntax of both types of CASE expressions:

CASE value WHEN target_value THEN result 
   WHEN target_value THEN result
   WHEN target_value THEN result
   ...
   ELSE result
   END 

CASE WHEN condition THEN result 
   WHEN condition THEN result 
   WHEN condition THEN result 
   ...
   ELSE result
   END 

The tutorial exercise below gives two good examples:

SELECT CASE 'Sun' WHEN 'Mon' THEN 'Open' 
   WHEN "Fri" THEN "Open" ELSE 'Closed' END FROM DUAL;
   Closed

SELECT CASE WHEN HOUR(CURRENT_TIME())<9 THEN 'Closed' 
   WHEN HOUR(CURRENT_TIME())>17 THEN 'Closed' 
   ELSE 'Open' END FROM DUAL;
   Closed

  1. What Is SQL Standard?
  2. How Many Groups of Data Types?
  3. What Are Character String Data Types?
  4. What Are the Differences between CHAR and NCHAR?
  5. What Are the Differences between CHAR and VARCHAR?
  6. What Are the Differences between BINARY and VARBINARY?
  7. What Are Numeric Data Types?
  8. What Are Date and Time Data Types?
  9. How To Calculate Expressions with SELECT Statements?
  10. How To Include Comments in SQL Statements?
  11. How To Include Character Strings in SQL statements?
  12. How To Escape Special Characters in SQL statements?
  13. How To Concatenate Two Character Strings?
  14. How To Include Numeric Values in SQL statements?
  15. How To Enter Characters as HEX Numbers?
  16. How To Enter Numeric Values as HEX Numbers?
  17. How To Enter Binary Numbers in SQL Statements?
  18. How To Enter Boolean Values in SQL Statements?
  19. What Are NULL Values?
  20. What Happens If NULL Values Are Involved in Expressions?
  21. How To Convert Numeric Values to Character Strings?
  22. How To Convert Character Strings to Numeric Values?
  23. How To Use IN Conditions?
  24. How To Use LIKE Conditions?
  25. How To Use Regular Expression in Pattern Match Conditions?
  26. How To Use CASE Expression?

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