documentationlead_not_null¶
Description¶
Return the non-null value of one column in a following row across an ordered group.
offset is the number of rows forward from the current row to obtain a
value, and any null value does not count towards the offset. The function can
still return null if no non-null value is found in the window frame. If no
ordering is specified, the default ordering is that of the invoking verb, which
is generally the valid_from timestamp, ascending. In this case,
lead_not_null(col, 1) returns the next non-null value for column col.
Return type¶
storable value
Domain¶
This is a window function (calculates over a group of multiple input rows using windowing.)
Categories¶
Usage¶
lead_not_null(expression, leadby)
Argument |
Type |
Optional |
Repeatable |
Restrictions |
|---|---|---|---|---|
expression |
storable value |
no |
no |
none |
leadby |
int64 |
no |
no |
constant |
Examples¶
make_col next_value:window(lead_not_null(value, 1), group_by(key))
Obtain the next non-null value within the group identified by key and store
the results in a new column named next_value.
timestamp |
key |
value |
next_value |
|---|---|---|---|
100 |
A |
5 |
3 |
150 |
B |
6 |
5 |
180 |
A |
null |
3 |
200 |
A |
null |
3 |
300 |
B |
5 |
null |
400 |
A |
3 |
null |