# Inverse distribution functions family syntax

The syntax for the inverse distribution functions family is as
follows:

```
SELECT fn(<expr>) WITHIN GROUP(ORDER BY <value_expression> [asc|desc]
[nulls {first | last}]) FROM <from_expr>[GROUP BY <group_expr>];
```

- percentile_cont (expr)
- This is computed by considering the pair of consecutive rows that
are indicated by the argument, treated as a fraction of the total
number of rows in the group, and interpolating the value of the value
expression that is evaluated for these rows. The interpolated value
x is obtained by using argument y. It is the one-sided inverse of percent_rank,
and can be used only with numeric and interval data types. This is
computed as follows:
`X = xf( rc-r) + xc( r –rf)`

Where- Y is the argument to the function
- r = Y *(N-1) + 1
- N is the number of values in the ordered partition/group
- rf = floor(r), rc=ceil(r)
- xf = value of order by column at row rf
- xc = value of order by column at rc

- percentile_disc (expr)
- This is computed by treating the group as a window partition of
the CUME_DIST window function by using the specified ordering of the
value expression as the window ordering, and returning the first value
expression whose cumulative distribution value is greater than or
equal to the argument. Works with all data types.

Where`X =xc`

- r = Y*N
- rc = ceil(r)
- xc is value of order by column at row rc

Note: The value of percentile_disc(0) is null.