SQL possible to display (only display) a non-date string in a date column?

I wondered if its possible to show a "-" whenever there is no date in a date column?

So one tuple might be {Dave, 13th July 2011}, whereas another could be {John,-}

EDIT: Thanks to the person below who suggested this:

SELECT `ID`, COALESCE(CAST(开发者_如何学JAVA`Graduation Date` AS CHAR), '-') FROM <table>

It worked!

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Use COALESCE?

SELECT name, COALESCE(date, '-')
FROM table

EDIT: Don't see how it is possible that it doesn't work. Example:

SELECT COALESCE('2011-01-01', '-') //returns '2011-01-01'
SELECT COALESCE('', '-') //returns ''
SELECT COALESCE(NULL, '-') //returns '-'

Try them 3 statements and you will see what is returned.

EDIT2:

SELECT name, IF(COALESCE(date, '-') = '', '-', date)
FROM table

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If your date column contains some special dates that you would like to treat in the same way as NULLs (for example, 0000-00-00), you could try this method:

SELECT COALESCE(NULLIF(yourdatecolumn, '0000-00-00'), '-')

That is essentially just a shorter way of writing this:

SELECT CASE
         WHEN yourdatecolumn IS NULL OR yourdatecolumn = '0000-00-00' THEN '-'
         ELSE yourdatecolumn
       END

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SELECT ID, IF(GRADUATIONDATE IS NULL, '-', GRADUATIONDATE) FROM TABLE

or 

SELECT ID, IFNULL(GRADUATIONDATE,'-') FROM TABLE