2.2 KiB
| toc_priority | toc_title |
|---|---|
| 62 | Window Functions |
[experimental] Window Functions
!!! warning "Warning"
This is an experimental feature that is currently in development and is not ready
for general use. It will change in unpredictable backwards-incompatible ways in
the future releases. Set allow_experimental_window_functions = 1 to enable it.
ClickHouse supports the standard grammar for defining windows and window functions. The following features are currently supported:
| Feature | Support or workaround |
|---|---|
ad hoc window specification (count(*) over (partition by id order by time desc)) |
yes |
WINDOW clause (select ... from table window w as (partiton by id)) |
yes |
ROWS frame |
yes |
RANGE frame |
yes, it is the default |
GROUPS frame |
no |
Calculating aggregate functions over a frame (sum(value) over (order by time)) |
all aggregate functions are supported |
rank(), dense_rank(), row_number() |
yes |
lag/lead(value, offset) |
no, replace with any(value) over (.... rows between <offset> preceding and <offset> preceding), or following for lead |
References
GitHub Issues
The roadmap for the initial support of window functions is in this issue.
All GitHub issues related to window funtions have the comp-window-functions tag.
Tests
These tests contain the examples of the currently supported grammar:
https://github.com/ClickHouse/ClickHouse/blob/master/tests/performance/window_functions.xml
Postgres Docs
https://www.postgresql.org/docs/current/sql-select.html#SQL-WINDOW
https://www.postgresql.org/docs/devel/sql-expressions.html#SYNTAX-WINDOW-FUNCTIONS
https://www.postgresql.org/docs/devel/functions-window.html
https://www.postgresql.org/docs/devel/tutorial-window.html
MySQL Docs
https://dev.mysql.com/doc/refman/8.0/en/window-function-descriptions.html
https://dev.mysql.com/doc/refman/8.0/en/window-functions-usage.html
https://dev.mysql.com/doc/refman/8.0/en/window-functions-frames.html