function(SELECT x, y ...) doesn't work

Using MySQL, I am trying to make a query less verbose. Instead of

UPDATE tbl SET col = Point(
    If(
        condition,
        long CASE WHEN THEN ELSE END,
        a different long CASE WHEN THEN ELSE END
    ),
    If(
        condition,
        long CASE WHEN THEN ELSE END,
        a different long CASE WHEN THEN ELSE END
    )
)

I tried the following but failed

UPDATE tbl SET col = Point(
    SELECT If(condition, x, different(x)), If(condition, y, different(y)) 
    FROM (
        SELECT long CASE WHEN THEN ELSE END x, long CASE WHEN THEN ELSE END y 
        FROM tbl
    ) foo
)

Is it not possible to use a SEL开发者_如何学GoECT statement to replace arguments to a function? Or, am I just doing something silly? Or, is there another way to make this long CASE WHEN THEN ELSE END appear only once?

Use something like:

UPDATE tbl AS m_tbl
SET col = (
    SELECT Point( IF(.., x1, x2), 
        IF (.., y1, y2)
    )
    FROM (
        SELECT .. AS x1, 
            .. AS x2, 
            .. AS y1, 
            .. AS y2
        FROM tbl
        WHERE m_tbl.pk_col = tbl.pk_col
    )
)

You could try to build your query along the lines of

UPDATE tbl
  INNER JOIN (
    SELECT
      tblKey,
      long CASE WHEN THEN ELSE END x,
      long CASE WHEN THEN ELSE END y 
    FROM tbl
  ) s ON tbl.tblKey = s.tblKey
SET tbl.col = Point(
  IF(condition, s.x, different(s.x)),
  IF(condition, s.y, different(s.y))
)