Ecto v3.1.0 Ecto.Query.WindowAPI View Source
Lists all windows functions.
Windows functions must always be used as the first argument
of over/2 where the second argument is the name of a window:
from e in Employee,
select: {e.depname, e.empno, e.salary, over(avg(e.salary), :department)},
windows: [department: [partition_by: e.depname]]In the example above, we get the average salary per department.
:department is the window name, partitioned by e.depname
and avg/1 is the window function.
However, note that defining a window is not necessary, as the
window definition can be given as the second argument to over:
from e in Employee,
select: {e.depname, e.empno, e.salary, over(avg(e.salary), partition_by: e.depname)}Both queries are equivalent. However, if you are using the same
partitioning over and over again, defining a window will reduce
the query size. See Ecto.Query.windows/3 for all possible window
expressions, such as :partition_by and :order_by.
Link to this section Summary
Functions
Calculates the average for the given entry.
Counts the entries in the table.
Counts the given entry.
Returns relative rank of the current row: (number of rows preceding or peer with current row) / (total rows).
Returns rank of the current row without gaps; this function counts peer groups.
Returns value evaluated at the row that is the first row of the window frame.
Returns value evaluated at the row that is offset rows before the current row within the partition.
Returns value evaluated at the row that is the last row of the window frame.
Returns value evaluated at the row that is offset rows after the current row within the partition.
Calculates the maximum for the given entry.
Calculates the minimum for the given entry.
Returns value evaluated at the row that is the nth row of the window
frame (counting from 1); nil if no such row.
Returns integer ranging from 1 to the argument value, dividing the partition as equally as possible.
Returns relative rank of the current row: (rank - 1) / (total rows - 1).
Returns rank of the current row with gaps; same as row_number/0 of its first peer.
Returns number of the current row within its partition, counting from 1.
Calculates the sum for the given entry.
Link to this section Functions
avg(value) View Source
Calculates the average for the given entry.
from p in Payment, select: avg(p.value)count() View Source
Counts the entries in the table.
from p in Post, select: count()count(value) View Source
Counts the given entry.
from p in Post, select: count(p.id)cume_dist() View Source
Returns relative rank of the current row: (number of rows preceding or peer with current row) / (total rows).
from p in Post,
select: cume_dist() |> over(partition_by: p.category_id, order_by: p.date)Note that this function must be invoked using window function syntax.
dense_rank() View Source
Returns rank of the current row without gaps; this function counts peer groups.
from p in Post,
select: dense_rank() |> over(partition_by: p.category_id, order_by: p.date)Note that this function must be invoked using window function syntax.
first_value(value) View Source
Returns value evaluated at the row that is the first row of the window frame.
from p in Post,
select: first_value(p.id) |> over(partition_by: p.category_id, order_by: p.date)Note that this function must be invoked using window function syntax.
lag(value, offset \\ 1, default \\ nil) View Source
Returns value evaluated at the row that is offset rows before the current row within the partition.
If there is no such row, instead return default (which must be of the
same type as value). Both offset and default are evaluated with respect
to the current row. If omitted, offset defaults to 1 and default to nil.
from e in Events,
windows: [w: [partition_by: e.name, order_by: e.tick]],
select: {
e.tick,
e.action,
e.name,
lag(e.action) |> over(:w), # previous_action
lead(e.action) |> over(:w) # next_action
}Note that this function must be invoked using window function syntax.
last_value(value) View Source
Returns value evaluated at the row that is the last row of the window frame.
from p in Post,
select: last_value(p.id) |> over(partition_by: p.category_id, order_by: p.date)Note that this function must be invoked using window function syntax.
lead(value, offset \\ 1, default \\ nil) View Source
Returns value evaluated at the row that is offset rows after the current row within the partition.
If there is no such row, instead return default (which must be of the
same type as value). Both offset and default are evaluated with respect
to the current row. If omitted, offset defaults to 1 and default to nil.
from e in Events,
windows: [w: [partition_by: e.name, order_by: e.tick],
select: {
e.tick,
e.action,
e.name,
lag(e.action) |> over(:w), # previous_action
lead(e.action) |> over(:w) # next_action
}Note that this function must be invoked using window function syntax.
max(value) View Source
Calculates the maximum for the given entry.
from p in Payment, select: max(p.value)min(value) View Source
Calculates the minimum for the given entry.
from p in Payment, select: min(p.value)nth_value(value, nth) View Source
Returns value evaluated at the row that is the nth row of the window
frame (counting from 1); nil if no such row.
from p in Post,
select: nth_value(p.id, 4) |> over(partition_by: p.category_id, order_by: p.date)Note that this function must be invoked using window function syntax.
ntile(num_buckets) View Source
Returns integer ranging from 1 to the argument value, dividing the partition as equally as possible.
from p in Post,
select: ntile(10) |> over(partition_by: p.category_id, order_by: p.date)Note that this function must be invoked using window function syntax.
percent_rank() View Source
Returns relative rank of the current row: (rank - 1) / (total rows - 1).
from p in Post,
select: percent_rank() |> over(partition_by: p.category_id, order_by: p.date)Note that this function must be invoked using window function syntax.
rank() View Source
Returns rank of the current row with gaps; same as row_number/0 of its first peer.
from p in Post,
select: rank() |> over(partition_by: p.category_id, order_by: p.date)Note that this function must be invoked using window function syntax.
row_number() View Source
Returns number of the current row within its partition, counting from 1.
from p in Post,
select: row_number() |> over(partition_by: p.category_id, order_by: p.date)Note that this function must be invoked using window function syntax.
sum(value) View Source
Calculates the sum for the given entry.
from p in Payment, select: sum(p.value)