如何在 Bigquery 循环中使用解码语句？ [重复]

Question

我在 Oracle 中编写了一个查询，现在需要将其转换为大查询格式，我对大查询非常陌生，需要您的帮助

(to_char(解码(符号(解码(to_char(c.last_updated_time +3, 'D') ,7 , c.last_updated_time +5 ,1 ,c.last_updated_time +5, 2, c.last_updated_time +5,3, c .last_updated_time +4, c.last_updated_time +3) -sysdate),-1,3,1)),' ') 优先级

Answer 1

首先我们用

last_updated_time

生成一些样本数据。

due_date

是几天后，具体取决于星期几。所以模拟一个周末和工作日。因此，添加到

last_updated_time

是通过

TIMESTAMP_ADD

完成的。由于

Interval

是 根据星期几（从 1 到 7 的数字），使用以下语句：

CASE day_of_the_week WHEN 7 then adding_value ... end

接下来计算

due_date

与今天之间的日期差。 Prio 1 代表过去的

due_date

。否则返回Prio 3。 所以我们最终得到这个 BigQuery 查询：

WITH
  tbl AS (
  SELECT * 
  from unnest(generate_timestamp_array(timestamp "2024-01-01",timestamp "2024-04-01",interval 1 day ) ) as last_updated_time
     )
SELECT *,
  IF(
    TIMESTAMP_DIFF(TIMESTAMP_ADD( c.last_updated_time, INTERVAL (
      CASE EXTRACT(DAYOFWEEK FROM TIMESTAMP_ADD(c.last_updated_time, INTERVAL 3 DAY))
        WHEN 7 THEN 5
        WHEN 1 THEN 4
        WHEN 2 THEN 4
        WHEN 3 THEN 4
      ELSE 3
    END
      ) DAY ),current_timestamp(), DAY)
      >0,3,1) # Prio 1 if day is in past, otherwise Prio 3 
     ||' ' # convert to string with space after
       AS Priority,
  CASE
    WHEN EXTRACT(DAYOFWEEK FROM TIMESTAMP_ADD(c.last_updated_time, INTERVAL 3 DAY)) = 7 THEN 
      TIMESTAMP_ADD(c.last_updated_time, INTERVAL 5 DAY)
    WHEN EXTRACT(DAYOFWEEK FROM TIMESTAMP_ADD(c.last_updated_time, INTERVAL 3 DAY)) IN (1, 2, 3) THEN 
      TIMESTAMP_ADD(c.last_updated_time, INTERVAL 4 DAY)
  ELSE
    TIMESTAMP_ADD(c.last_updated_time, INTERVAL 3 DAY)
END
  AS due_date
FROM
  tbl AS c
  order by 1

如您所见，另一种解决方案用于所呈现的

due_date

。之前先完成星期几的案例陈述，然后对每个案例进行日期计算。

我还想评论给定 Oracle 查询的每一步：

-- query with comments above each line
SELECT 
    -- convert result to string and add a space character
    TO_CHAR(
        -- The DECODE(x,1,2) function is the (CASE x when 1 then 2 end) structure in BigQuery
        DECODE(
            -- This SIGN function returns -1 if the value is negative, 0 if zero, and 1 if positive
            SIGN(
                -- This DECODE function calculates a due date based on the last_updated_time and this date of the week
                DECODE(
                    -- TO_CHAR function converts last_updated_time + 3 days into the day of the week
                    TO_CHAR(c.last_updated_time + 3, 'D'),  
                    -- If day of the week is Saturday (7), add 5 days
                    7, c.last_updated_time + 5,
                    -- If day of the week is Sunday (1), add 5 days
                    1, c.last_updated_time + 5,
                    -- If day of the week is Monday (2), add 5 days
                    2, c.last_updated_time + 5,
                    -- If day of the week is Tuesday (3), add 4 days
                    3, c.last_updated_time + 4,
                    -- For all other days, add 3 days
                    c.last_updated_time + 3
                ) - SYSDATE -- Subtracting current system date
            ),
            -- If the result is negative, return prio 3 (due date is today or in the future)
            -1, 3,
            -- If the result is positive or zero, return prio 1 (due date is in the past)
            1
        ),
        ' ' -- Convert the result into a character string with a space character
    ) AS Priority
FROM tbl AS c;