COALESCE 内的 Clickhouse leadInFrame return 未知标识符

Question

我正在关注 Altinity 关于如何实现 Lag/Lead 函数的示例 https://kb.altinity.com/altinity-kb-queries-and-syntax/lag-lead/ 但是我找不到用其他值替换 NULLs 的方法。

使用该示例并添加 toNullable(a)，您可以看到许多值将变为 NULL。

SELECT
    g,
    a,
    lagInFrame(toNullable(a)) OVER (PARTITION BY g ORDER BY a ASC Rows BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS prev,
    leadInFrame(a) OVER (PARTITION BY g ORDER BY a ASC Rows BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS next
FROM llexample
ORDER BY
    g ASC,
    a ASC

Query id: 65c75108-520f-4115-8996-328e8e62aa25

┌─g─┬──────────a─┬───────prev─┬───────next─┐
│ 0 │ 2020-01-01 │       ᴺᵁᴸᴸ │ 2020-01-04 │
│ 0 │ 2020-01-04 │ 2020-01-01 │ 2020-01-07 │
│ 0 │ 2020-01-07 │ 2020-01-04 │ 2020-01-10 │
│ 0 │ 2020-01-10 │ 2020-01-07 │ 1970-01-01 │
│ 1 │ 2020-01-02 │       ᴺᵁᴸᴸ │ 2020-01-05 │
│ 1 │ 2020-01-05 │ 2020-01-02 │ 2020-01-08 │
│ 1 │ 2020-01-08 │ 2020-01-05 │ 1970-01-01 │
│ 2 │ 2020-01-03 │       ᴺᵁᴸᴸ │ 2020-01-06 │
│ 2 │ 2020-01-06 │ 2020-01-03 │ 2020-01-09 │
│ 2 │ 2020-01-09 │ 2020-01-06 │ 1970-01-01 │
└───┴────────────┴────────────┴────────────┘

我试图在 COALESCE 中添加 leadInFrame。但是当我尝试这样做时，我得到了错误：

SELECT
    g,
    a,
    COALESCE(
      lagInFrame(toNullable(a)) OVER (PARTITION BY g ORDER BY a ASC Rows BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
      today()
    ) AS prev,
    leadInFrame(a) OVER (PARTITION BY g ORDER BY a ASC Rows BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS next
FROM llexample
ORDER BY
    g ASC,
    a ASC

Query id: 9685b822-7f31-45d3-9103-89f06b373876


0 rows in set. Elapsed: 0.002 sec.

Received exception from server (version 22.1.2):
Code: 47. DB::Exception: Received from localhost:9000. DB::Exception: Unknown identifier: lagInFrame(toNullable(a)) OVER (PARTITION BY g ORDER BY a ASC Rows BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING); there are columns: g, a, toNullable(a): While processing g, a, coalesce(lagInFrame(toNullable(a)) OVER (PARTITION BY g ORDER BY a ASC Rows BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING), today()) AS prev, leadInFrame(a) OVER (PARTITION BY g ORDER BY a ASC Rows BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS next. (UNKNOWN_IDENTIFIER)

我也尝试了其他条件，但得到了同样的错误。

最佳

Answer 1

https://github.com/ClickHouse/ClickHouse/issues/19857 您只需要使用子查询，因为 window 函数还没有完全发挥作用。

select 
  g,
  a,
  COALESCE( prev,  today()) prev,
  next
from (  
    SELECT
        g,
        a,
        lagInFrame(toNullable(a)) OVER (PARTITION BY g ORDER BY a ASC Rows BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) prev,
        leadInFrame(a) OVER (PARTITION BY g ORDER BY a ASC Rows BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS next
    FROM llexample
    ORDER BY
        g ASC,
        a ASC
)

COALESCE 内的 Clickhouse leadInFrame return 未知标识符

Clickhouse leadInFrame inside COALESCE return Unknown identifier

clickhouse