Window Functions
cume_dist
Returns the cumulative distribution of a value in a group of values. The result is the number of rows preceding or peer with the row in the window ordering of the window partition divided by the total number of rows in the window partition. Thus, any tie values in the ordering will evaluate to the same distribution value.
Supported Signatures
function cume_dist() returns double
dense_rank
Returns the rank of a value in a group of values. This is similar to rank(), except that tie values do not produce gaps in the sequence.
Examples:
SELECT name, DENSE_RANK() OVER (ORDER BY score) AS dense_rank_col FROM (
VALUES ('A', 10), ('B', 20), ('C', 20), ('D', 30)
) AS t (name, score)
-- value '('A', 1), ('B', 2), ('C', 2), ('D', 3)'
Supported Signatures
function dense_rank() returns bigint
first_value
Returns the first value of the window.
Supported Signatures
function first_value($1) returns $1
lag
Returns the value at offset rows before the current row in the window partition. Offsets start at 0, which is the current row. The offset can be any scalar expression. The default offset is 1. If the offset is null, an error is raised. If the offset refers to a row that is not within the partition, the default_value is returned, or if it is not specified null is returned. The lag() function requires that the window ordering be specified. Window frame must not be specified.
Examples:
SELECT name, score, LAG(score) OVER (PARTITION BY name) AS lead_score FROM (
VALUES ('A', 10), ('A', 20), ('D', 20), ('D', 30)
) AS t (name, score)
-- value '('A', 10, ), ('A', 20, 10), ('D', 20, ), ('D', 30, 20)'
Supported Signatures
function lag($1) returns $1
function lag($1, bigint) returns $1
function lag($1, bigint, $1) returns $1
last_value
Returns the last value of the window.
Supported Signatures
function last_value($1) returns $1
lead
Returns the value at offset rows after the current row in the window partition. Offsets start at 0, which is the current row. The offset can be any scalar expression. The default offset is 1. If the offset is null, an error is raised. If the offset refers to a row that is not within the partition, the default_value is returned, or if it is not specified null is returned. The lead() function requires that the window ordering be specified. Window frame must not be specified.
Examples:
SELECT name, score, LEAD(score) OVER (PARTITION BY name) AS lead_score FROM (
VALUES ('A', 10), ('A', 20), ('D', 20), ('D', 30)
) AS t (name, score)
-- value '('A', 10, 20), ('A', 20, ), ('D', 20, 30), ('D', 30, )'
Supported Signatures
function lead($1) returns $1
function lead($1, bigint) returns $1
function lead($1, bigint, $1) returns $1
nth_value
Returns the value at the specified offset from the beginning of the window. Offsets start at 1. The offset can be any scalar expression. If the offset is null or greater than the number of values in the window, null is returned. It is an error for the offset to be zero or negative.
Supported Signatures
function nth_value($1, bigint) returns $1
ntile
Divides the rows for each window partition into n buckets ranging from 1 to at most n. Bucket values will differ by at most 1. If the number of rows in the partition does not divide evenly into the number of buckets, then the remainder values are distributed one per bucket, starting with the first bucket.
Examples:
SELECT name, NTILE(5) OVER (ORDER BY score) AS ntile_col FROM (
VALUES ('A', 10), ('A', 20), ('A', 30), ('A', 40)
) AS t (name, score)
-- value '('A', 1), ('A', 2), ('D', 3), ('D', 4)'
Supported Signatures
function ntile(bigint) returns bigint
percent_rank
Returns the percentage ranking of a value in group of values. The result is (r - 1) / (n - 1) where r is the rank() of the row and n is the total number of rows in the window partition.
Examples:
SELECT name, PERCENT_RANK() OVER (ORDER BY score) AS percent_rank_col FROM (
VALUES ('A', 10), ('B', 20), ('C', 20), ('D', 30)
) AS t (name, score)
-- value '('A', 0.0), ('B', 0.33333333), ('C', 0.33333333), ('D', 1.0)'
Supported Signatures
function percent_rank() returns double
rank
Returns the rank of a value in a group of values. The rank is one plus the number of rows preceding the row that are not peer with the row. Thus, tie values in the ordering will produce gaps in the sequence. The ranking is performed for each window partition.
Examples:
SELECT name, RANK() OVER (ORDER BY score) AS rank_col FROM (
VALUES ('A', 10), ('B', 20), ('C', 20), ('D', 30)
) AS t (name, score)
-- value '('A', 1), ('B', 2), ('C', 2), ('D', 4)'
Supported Signatures
function rank() returns bigint
row_number
Returns a unique, sequential number for each row, starting with one, according to the ordering of rows within the window partition.
Examples:
SELECT name, ROW_NUMBER() OVER (ORDER BY score) AS row_number_col FROM (
VALUES ('A', 10), ('B', 20), ('C', 20), ('D', 30)
) AS t (name, score)
-- value '('A', 1), ('B', 2), ('C', 3), ('D', 4)'
Supported Signatures
function row_number() returns bigint