MYSQL IF(expr1,expr2,expr3) but I don’t want any expr3 (if expr3 then don’t output anything

As the title says, I just want an output if the if is matched, if it’s not matched then I don’t want any output.

I currently have this, but it gives an error ob开发者_开发百科viously

...rFormat=IF(ISNULL(rFormat), VALUES(rFormat),UNCHANGED)…

I looked around http://dev.mysql.com/doc/refman/5.4/en/control-flow-functions.html but didn’t really find out how to do it.

This question is kinda related to Only update the MYSQL field if the field contains null or 0

This is used in context of: (as seen in the above URL)

………
ON DUPLICATE KEY UPDATE
rFormat=VALUES(rFormat),
rFiles=IF(ISNULL(rFiles), VALUES(rFiles), VALUES(rSizeMB)),
rText=VALUES(rText);

You could simply do

IF(ISNULL(rFormat), VALUES(rFormat), rFormat)

I'm not sure what you are trying to achieve by calling VALUES() at this point, however.

Just use WHERE rFormat IS NULL instead of IF.

Try this:

rFiles = COALESCE(existingColumnValue,'$newValue')

COALESCE returns the first non-null value. Note that you will need quotes around the $newValue if it is a string, and don't forget to escape. You won't use the quotes around the column name (existingColumnValue). If you are also looking for rows that have a (INT) 0 as the value as well as NULL, you might want to try this:

rFiles = CASE existingColumnValue WHEN NULL THEN '$newValue' WHEN 0 THEN '$newValue' ELSE existingColumnValue END CASE

I had to change your column names so that I could better express the solution. I hope that you still understand. I was assuming that the $newValue is not another column in the database, but a variable being passed from your script.