Postgresql generate_series動態區間

Question

您好我想在Postgresql中使用generate_series進行動態時間序列。

例如，我有一組隨機日期列表：

cleaning date 
2015-03-01 00:00 
2015-05-31 00:00 
2015-06-13 00:00 

，我想通過這些清洗日期動態分手的日期時間。

其結果將是這樣的：

start date   end date 
0000-00-00 00:00 2015-03-01 00:00 
2015-03-01 00:00 2015-05-31 00:00 
2015-05-31 00:00 2015-06-13 00:00 
2015-06-13 00:00 (current_timestamp) 

我有不知道如何我設置在generate_series動態區間... 那是可以通過generate_series？

Answer 1

我真的沒有看到使用generate_series的一點。

爲了得到結果，你提出你可以使用ROW_NUMBER和自聯接：

CREATE TABLE tab(cleaning timestamp); 

INSERT INTO tab(cleaning) 
VALUES ('2015-03-01 00:00'), ('2015-05-31 00:00'), ('2015-06-13 00:00'); 

主查詢：

WITH cte AS 
(
    SELECT cleaning, ROW_NUMBER() OVER(ORDER BY cleaning) AS rn 
    FROM tab 
) 
SELECT COALESCE(c1.cleaning,'0001-01-01'::timestamp) AS start_date, 
     COALESCE(c2.cleaning,CURRENT_TIMESTAMP) AS end_date 
FROM cte c1 
FULL JOIN cte c2 
    ON c1.rn = c2.rn-1 
ORDER BY start_date; 

SqlFiddleDemo

輸出：

╔═══════════════════════════╦═════════════════════════╗ 
║  start_date   ║  end_date   ║ 
╠═══════════════════════════╬═════════════════════════╣ 
║ January, 01 0001 00:00:00 ║ March, 01 2015 00:00:00 ║ 
║ March, 01 2015 00:00:00 ║ May, 31 2015 00:00:00 ║ 
║ May,  31 2015 00:00:00 ║ June, 13 2015 00:00:00 ║ 
║ June, 13 2015 00:00:00 ║ March, 30 2016 11:03:38 ║ 
╚═══════════════════════════╩═════════════════════════╝ 

編輯：

另一種可能性是使用LAG/LEAD窗口功能：

SELECT COALESCE(LAG(cleaning) OVER(ORDER BY cleaning), '0001-01-01'::timestamp) 
     AS start_date 
     ,cleaning AS end_date 
FROM tab 
UNION ALL 
SELECT MAX(cleaning), CURRENT_TIMESTAMP 
FROM tab 
ORDER BY start_date; 

SqlFiddleDemo2