Ecto v3.0.6 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); null 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
Calculates the average for the given entry.
from p in Payment, select: avg(p.value)Counts the entries in the table.
from p in Post, select: count()Counts the given entry.
from p in Post, select: count(p.id)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.
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.
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.
Returns value evaluated at the row that is offset rows before the current row within the partition.
Ff 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 null.
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.
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.
Returns value evaluated at the row that is offset rows after the current row within the partition.
Ff 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 null.
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.
Calculates the maximum for the given entry.
from p in Payment, select: max(p.value)Calculates the minimum for the given entry.
from p in Payment, select: min(p.value)Returns value evaluated at the row that is the nth row of the window frame (counting from 1); null 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.
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.
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.
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.
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.
Calculates the sum for the given entry.
from p in Payment, select: sum(p.value)