[Fix](variance) Fix sample variance/stddev null res for single value#3765
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zclllyybb
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…63605) Problem Summary: Fix `VAR_SAMP`, `VARIANCE_SAMP`, and `STDDEV_SAMP` to return `NaN` when the number of valid input values is less than or equal to 1. Sample variance/stddev are undefined for `n <= 1`, so returning `0.0` is misleading. before: ```sql CREATE TABLE t (id INT, v DOUBLE) DUPLICATE KEY(id) DISTRIBUTED BY HASH(id) BUCKETS 1 PROPERTIES('replication_num'='1'); INSERT INTO t VALUES (1, 5.0); -- 单行 SELECT VAR_SAMP(v), STDDEV_SAMP(v) FROM t; +-------------+----------------+ | VAR_SAMP(v) | STDDEV_SAMP(v) | +-------------+----------------+ | 0 | 0 | +-------------+----------------+ ``` now: ```sql SELECT VAR_SAMP(v), STDDEV_SAMP(v) FROM t; +-------------+----------------+ | VAR_SAMP(v) | STDDEV_SAMP(v) | +-------------+----------------+ | NaN | NaN | +-------------+----------------+ ``` doc: apache/doris-website#3765
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linrrzqqq
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…pache#63605) Problem Summary: Fix `VAR_SAMP`, `VARIANCE_SAMP`, and `STDDEV_SAMP` to return `NaN` when the number of valid input values is less than or equal to 1. Sample variance/stddev are undefined for `n <= 1`, so returning `0.0` is misleading. before: ```sql CREATE TABLE t (id INT, v DOUBLE) DUPLICATE KEY(id) DISTRIBUTED BY HASH(id) BUCKETS 1 PROPERTIES('replication_num'='1'); INSERT INTO t VALUES (1, 5.0); -- 单行 SELECT VAR_SAMP(v), STDDEV_SAMP(v) FROM t; +-------------+----------------+ | VAR_SAMP(v) | STDDEV_SAMP(v) | +-------------+----------------+ | 0 | 0 | +-------------+----------------+ ``` now: ```sql SELECT VAR_SAMP(v), STDDEV_SAMP(v) FROM t; +-------------+----------------+ | VAR_SAMP(v) | STDDEV_SAMP(v) | +-------------+----------------+ | NaN | NaN | +-------------+----------------+ ``` doc: apache/doris-website#3765
linrrzqqq
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Jun 1, 2026
…pache#63605) Problem Summary: Fix `VAR_SAMP`, `VARIANCE_SAMP`, and `STDDEV_SAMP` to return `NaN` when the number of valid input values is less than or equal to 1. Sample variance/stddev are undefined for `n <= 1`, so returning `0.0` is misleading. before: ```sql CREATE TABLE t (id INT, v DOUBLE) DUPLICATE KEY(id) DISTRIBUTED BY HASH(id) BUCKETS 1 PROPERTIES('replication_num'='1'); INSERT INTO t VALUES (1, 5.0); -- 单行 SELECT VAR_SAMP(v), STDDEV_SAMP(v) FROM t; +-------------+----------------+ | VAR_SAMP(v) | STDDEV_SAMP(v) | +-------------+----------------+ | 0 | 0 | +-------------+----------------+ ``` now: ```sql SELECT VAR_SAMP(v), STDDEV_SAMP(v) FROM t; +-------------+----------------+ | VAR_SAMP(v) | STDDEV_SAMP(v) | +-------------+----------------+ | NaN | NaN | +-------------+----------------+ ``` doc: apache/doris-website#3765
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