Question

说我有下表：

col
NULL
1
1
2

然后我选择：

SELECT col, DENSE_RANK() OVER(ORDER BY col) as rnk from table

然后我得到：

col  rnk
NULL 1
1    2
1    2
2    3

我想得到的是：

col  rnk
NULL NULL
1    1
1    1
2    2

但如果我查询：

SELECT col, CASE WHEN col IS NOT NULL THEN DENSE_RANK() OVER(ORDER BY col) END as rnk from table

然后我得到：

col  rnk
NULL NULL
1    2
1    2
2    3

除了使用NULL子句之外，有没有办法在排名时忽略WHERE？我有一些其他列，其行不能省略。

Answer 1

使用partition by：

SELECT col,
       (CASE WHEN col IS NOT NULL
             THEN DENSE_RANK() OVER (PARTITION BY (CASE WHEN col IS NOT NULL THEN 1 ELSE 2 END)
                                     ORDER BY col
                                    )
        END) as rnk
FROM table;

Answer 2

以下是BigQuery Legacy SQL

SELECT col, CASE WHEN col IS NOT NULL THEN rnk END AS rnk
FROM (
  SELECT 
    col, (col IS NULL) AS tmp, 
    DENSE_RANK() OVER(PARTITION BY tmp ORDER BY col) AS rnk 
  FROM table
)

如何在DENSE_RANK（）中不计算NULL值？

2 个答案: