WIDTH_BUCKET
描述
构造等宽直方图，其中直方图范围被划分为相同大小的区间，并在计算后返回表达式的值所在的桶号。特殊情况：
- 该函数返回一个整数值或空值（如果任何输入为空值则返回空值）。
语法
WIDTH_BUCKET(<expr>, <min_value>, <max_value>, <num_buckets>)
参数
| 参数 | 说明 |
|---|---|
<expr> | 创建直方图的表达式。此表达式必须计算为数值或可隐式转换为数值的值,此值的范围必须为 -(2^53 - 1) 到 2^53 - 1 (含) |
<min_value> | 表达式可接受范围的最低值点。参数必须为数值且不等于<max_value>，范围必须为 -(2^53 - 1) to 2^53 - 1 (含)). 此外，最高值点与最低值点的差必须小于 2^53 (例如： abs(max_value - min_value) < 2^53) |
<max_value> | 表达式可接受范围的最高值点。参数必须为数值且不等于<min_value>，范围必须为 -(2^53 - 1) to 2^53 - 1 (含)). 此外，最高值点与最低值点的差必须小于 2^53 (例如： abs(max_value - min_value) < 2^53) |
<num_buckets> | 分桶的数量，必须是正整数值。将表达式中的一个值分配给每个存储桶，然后该函数返回相应的存储桶编号 |
返回值
返回表达式值所在的桶号。当表达式超出范围时，函数返回规则如下：
- 如果表达式的值小于
min_value返回0. - 如果表达式的值大于或等于
max_value返回num_buckets + 1. - 如果任意参数为
null返回null.
举例
DROP TABLE IF EXISTS width_bucket_test;
CREATE TABLE IF NOT EXISTS width_bucket_test (
`k1` int NULL COMMENT "",
`v1` date NULL COMMENT "",
`v2` double NULL COMMENT "",
`v3` bigint NULL COMMENT ""
) ENGINE=OLAP
DUPLICATE KEY(`k1`)
DISTRIBUTED BY HASH(`k1`) BUCKETS 1
PROPERTIES (
"replication_allocation" = "tag.location.default: 1",
"storage_format" = "V2"
);
INSERT INTO width_bucket_test VALUES
(1, "2022-11-18", 290000.00, 290000),
(2, "2023-11-18", 320000.00, 320000),
(3, "2024-11-18", 399999.99, 399999),
(4, "2025-11-18", 400000.00, 400000),
(5, "2026-11-18", 470000.00, 470000),
(6, "2027-11-18", 510000.00, 510000),
(7, "2028-11-18", 610000.00, 610000),
(8, null, null, null);
SELECT * FROM width_bucket_test ORDER BY k1;
+------+------------+-----------+--------+
| k1 | v1 | v2 | v3 |
+------+------------+-----------+--------+
| 1 | 2022-11-18 | 290000 | 290000 |
| 2 | 2023-11-18 | 320000 | 320000 |
| 3 | 2024-11-18 | 399999.99 | 399999 |
| 4 | 2025-11-18 | 400000 | 400000 |
| 5 | 2026-11-18 | 470000 | 470000 |
| 6 | 2027-11-18 | 510000 | 510000 |
| 7 | 2028-11-18 | 610000 | 610000 |
| 8 | NULL | NULL | NULL |
+------+------------+-----------+--------+
SELECT k1, v1, v2, v3, width_bucket(v1, date('2023-11-18'), date('2027-11-18'), 4) AS w FROM width_bucket_test ORDER BY k1;
+------+------------+-----------+--------+------+
| k1 | v1 | v2 | v3 | w |
+------+------------+-----------+--------+------+
| 1 | 2022-11-18 | 290000 | 290000 | 0 |
| 2 | 2023-11-18 | 320000 | 320000 | 1 |
| 3 | 2024-11-18 | 399999.99 | 399999 | 2 |
| 4 | 2025-11-18 | 400000 | 400000 | 3 |
| 5 | 2026-11-18 | 470000 | 470000 | 4 |
| 6 | 2027-11-18 | 510000 | 510000 | 5 |
| 7 | 2028-11-18 | 610000 | 610000 | 5 |
| 8 | NULL | NULL | NULL | NULL |
+------+------------+-----------+--------+------+
SELECT k1, v1, v2, v3, width_bucket(v2, 200000, 600000, 4) AS w FROM width_bucket_test ORDER BY k1;
+------+------------+-----------+--------+------+
| k1 | v1 | v2 | v3 | w |
+------+------------+-----------+--------+------+
| 1 | 2022-11-18 | 290000 | 290000 | 1 |
| 2 | 2023-11-18 | 320000 | 320000 | 2 |
| 3 | 2024-11-18 | 399999.99 | 399999 | 2 |
| 4 | 2025-11-18 | 400000 | 400000 | 3 |
| 5 | 2026-11-18 | 470000 | 470000 | 3 |
| 6 | 2027-11-18 | 510000 | 510000 | 4 |
| 7 | 2028-11-18 | 610000 | 610000 | 5 |
| 8 | NULL | NULL | NULL | NULL |
+------+------------+-----------+--------+------+
SELECT k1, v1, v2, v3, width_bucket(v3, 200000, 600000, 4) AS w FROM width_bucket_test ORDER BY k1;
+------+------------+-----------+--------+------+
| k1 | v1 | v2 | v3 | w |
+------+------------+-----------+--------+------+
| 1 | 2022-11-18 | 290000 | 290000 | 1 |
| 2 | 2023-11-18 | 320000 | 320000 | 2 |
| 3 | 2024-11-18 | 399999.99 | 399999 | 2 |
| 4 | 2025-11-18 | 400000 | 400000 | 3 |
| 5 | 2026-11-18 | 470000 | 470000 | 3 |
| 6 | 2027-11-18 | 510000 | 510000 | 4 |
| 7 | 2028-11-18 | 610000 | 610000 | 5 |
| 8 | NULL | NULL | NULL | NULL |
+------+------------+-----------+--------+------+
