Home >> FAQs/Tutorials >> Oracle Tutorials

Oracle Tutorials - Use NULL as Conditions

By: FYIcenter.com

(Continued from previous topic...)

How To Use NULL as Conditions?

If you want to compare values against NULL as conditions, you should use the "IS NULL" or "IS NOT NULL" operator. Do not use "=" or "<>" against NULL. The sample script below shows you some good examples:

SELECT 'A' IS NULL FROM DUAL;
  -- Error: Boolean is not data type. 
  -- Boolean can only be used as conditions
  
SELECT CASE WHEN 'A' IS NULL THEN 'TRUE' ELSE 'FALSE' END
  FROM DUAL;
FALSE

SELECT CASE WHEN '' IS NULL THEN 'TRUE' ELSE 'FALSE' END
  FROM DUAL;
TRUE

SELECT CASE WHEN 0 IS NULL THEN 'TRUE' ELSE 'FALSE' END
  FROM DUAL;
FALSE

SELECT CASE WHEN NULL IS NULL THEN 'TRUE' ELSE 'FALSE' END
  FROM DUAL;
TRUE

SELECT CASE WHEN 'A' = NULL THEN 'TRUE' ELSE 'FALSE' END
  FROM DUAL;
  -- Do not use "="
FALSE

SELECT CASE WHEN 'A' <> NULL THEN 'TRUE' ELSE 'FALSE' END
  FROM DUAL;
  -- Do not use "<>"
FALSE

SELECT CASE WHEN NULL = NULL THEN 'TRUE' ELSE 'FALSE' END
  FROM DUAL;
  -- Do not use "="
FALSE

(Continued on next topic...)

  1. What Is SQL Standard?
  2. How Many Categories of Data Types?
  3. What Are the Oracle Built-in Data Types?
  4. What Are the Differences between CHAR and NCHAR?
  5. What Are the Differences between CHAR and VARCHAR2?
  6. What Are the Differences between NUMBER and BINARY_FLOAT?
  7. What Are the Differences between DATE and TIMESTAMP?
  8. What Are the Differences between INTERVAL YEAR TO MONTH and INTERVAL DAY TO SECOND?
  9. What Are the Differences between BLOB and CLOB?
  10. What Are the ANSI Data Types Supported in Oracle?
  11. How To Write Text Literals?
  12. How To Write Numeric Literals?
  13. How To Write Date and Time Literals?
  14. How To Write Date and Time Interval Literals?
  15. How To Convert Numbers to Character Strings?
  16. How To Convert Characters to Numbers?
  17. How To Convert Dates to Characters?
  18. How To Convert Character Strings to Dates?
  19. How To Convert Times to Character Strings?
  20. How To Convert Character Strings to Times?
  21. What Is NULL Value?
  22. How To Use NULL as Conditions?
  23. How To Concatenate Two Text Values?
  24. How To Increment Dates by 1?
  25. How To Calculate Date and Time Differences?
  26. How To Use IN Conditions?
  27. How To Use LIKE Conditions?
  28. How To Use Regular Expression in Pattern Match Conditions?

Oracle Tutorials:

More...


Other Tutorials/FAQs:

More...


Related Resources:

More...


Selected Jobs:

More...