IF statement in WHERE clause of MySQL Query

seems to me that you need a case expression within the select clause (this is the sql IF equivalent). Currently you are trying to embed some if conditions into the where clause (and IF isn't a sql thing).

I'm assuming partialDay is a field in the table.

$getAbsences = mysql_query("SELECT respid, startDate, 
 CASE WHEN partialDay = 1 THEN SUBSTRING(returnDate - INTERVAL 1 DAY, 1, 10) 
      WHEN partialDay = 0 THEN SUBSTRING(returnDate, 1, 10) 
 END  as returnDate 
 FROM fm_calendar_absenceRequest 
 WHERE SUBSTRING(startDate,1,10) <= '".date("Y-m-d", strtotime($dayChoice))."' 
 AND hidden = '0' AND requestApproved = '1'") or die("Check Time: " . mysql_error());

-- as straight sql it would look like this:

SELECT respid, startDate, 
 CASE WHEN partialDay = 1 THEN SUBSTRING(returnDate - INTERVAL 1 DAY, 1, 10) 
      WHEN partialDay = 0 THEN SUBSTRING(returnDate, 1, 10) 
 END  as returnDate 
 FROM fm_calendar_absenceRequest 
 WHERE SUBSTRING(startDate,1,10) <= '2013-06-24' 
 AND hidden = '0' AND requestApproved = '1'

Select all Open in new window

you might prefer to use 'else'

SELECT respid, startDate, 
 CASE WHEN partialDay = 1 THEN SUBSTRING(returnDate - INTERVAL 1 DAY, 1, 10) 
      ELSE SUBSTRING(returnDate, 1, 10) 
 END  as returnDate 
 FROM fm_calendar_absenceRequest 
 WHERE SUBSTRING(startDate,1,10) <= '2013-06-24' 
 AND hidden = '0' AND requestApproved = '1'

Select all Open in new window

See if this article can give you some clues about it.  If you want to post a few examples of the inputs and expected outputs, we may be able to give you a tested-and-working example.
http://www.experts-exchange.com/Web_Development/Web_Languages-Standards/PHP/A_201-Handling-date-and-time-in-PHP-and-MySQL.html

PortletPaul,

The query you had suggested returns ALL events prior to 6/24, instead of the 22 absences that it should be returning.

>> 22 absences that it should be returning.
I was trying to answering the following really:

"If it is a partial day off, I want to display the return date that is stored in the database, but if it is not a partial day< I want to pull one day less than the return date."
and for this you need something like the case expression I provided

To figure out "22 absences that it should be returning" would I guess require a change to the where clause - but I don't know you data.  How does one arrive at the 22 expected absences? (I can help translate that into sql if needed).

e.g. should the where clause be something like?
 WHERE SUBSTRING(startDate,1,10) >= '2013-06-01'
AND hidden = '0' AND requestApproved = '1'

bottom line: I'm guessing how to arrive at the 22 expected results
- & I didn't know that was part of the question

If you want to post a few examples of the inputs and expected outputs, we may be able to give you a tested-and-working example.

http://sscce.org/

Really, it's all about the data.

Sure, sorry.

Essentially we are trying to display the absences for that particular day.

There are different scenarios all of which I need to account for.

1.  If an employee took a partial day (which is a flag in the table), they need to show up for being off today.

2.  If an employees return date is today, then they shouldn't be, which is where I was trying to use the CASE statement for if its a partial day, then show up, but if its not a partial day, then somehow exclude that record from the result date, since they are back to work today.

3.  If an employee is out for an extended period of time, for example started their vacation on 6/22 and returns 7/1, they should appear on this list even though the start and end date is out of this range.

The report is currently done on another server, but the guy before me ran multiple queries and used PHP to help manipulate the data, where I was hoping for an all MySQL solution, but maybe thats not possible?  I'm not sure.

There are different scenarios all of which I need to account for.

If you can post some of the test data set that shows these different scenarios, we can almost certainly help you further.  Descriptions of the test data are almost always useless; the actual data is all we need.

An example of the data might take the form of a short script that created a temporary table and inserted the data into the table.  The SQL INSERT statements need not be many or complicated - just enough data to illustrate each of the scenarios you want to treat differently.

Armed with a little script that does those things, we can almost certainly show you tested and working code examples.  Thanks, ~Ray