Compatibility
TO_CHAR(d,'YYYY')
Engine	OK	Alternative
ingres	No	EXTRACT(HOUR from d)
mysql	No	EXTRACT(HOUR from d)
oracle	Yes
postgres	No	EXTRACT(HOUR from d)
sqlserver	No	DATEPART(HOUR,d)

TO_CHAR (dates)

TO_CHAR allows you to convert a date to a string using a variety of formats.

 TO_CHAR(d, 'YYYY') -> Four digit year
 TO_CHAR(d, 'MM')   -> Two digit month
 TO_CHAR(d, 'DD')   -> Two digit day
 TO_CHAR(d, 'HH24') -> Two digit hour
 TO_CHAR(d, 'MI')   -> Two digit minutes
 TO_CHAR(d, 'MON')  -> Three character month

In this example you get the month as a three character abbreviation and a four digit year from the date field whn.

SELECT DATEPART(YEAR from whn) AS v
      ,whn
      ,wht
  FROM eclipse

SELECT TO_CHAR(whn, 'MON YYYY') AS v
      ,whn
      ,wht
  FROM gisq.eclipse

SELECT EXTRACT(YEAR from whn) AS v, whn, wht
  FROM eclipse