PostgreSQL的 - 報告的第一和最後一個版本之間的時間差

Question

我report_history表的表結構如下：

CREATE TABLE "report_history"(
"pk"     SERIAL   PRIMARY KEY, 
"revision"   BIGINT, 
"report_fk"   BIGINT, 
"old_status_fk"  BIGINT, 
"updatedby_fk"  BIGINT, 
"updated_datetime" TIMESTAMP, 
"file_path"   TEXT, 
"synopsis"   TEXT 
); 

而report表本身的定義，像這樣：

CREATE TABLE "report"(
"pk"     SERIAL   PRIMARY KEY, 
"report_uuid"   VARCHAR(32)  UNIQUE, 
"study_fk"    BIGINT, 
"status_fk"    BIGINT, 
"priority_fk"   BIGINT, 
"report_relative_path" VARCHAR(256), 
"report_type_fk"  BIGINT, 
"createdby_fk"   BIGINT, 
"created_datetime"  TIMESTAMP 
); 

我想知道的是，我如何才能找到報告第一次修訂和同一報告最後一次修訂之間的差異（及時）？澄清，在pesudocode，我想執行以下減法：

RETURN report_history.updated_datetime (newest) - report_history.updated_datetime 
(oldest) WHERE report_fk = ? 

任何人都可以幫我解決這個問題嗎？提前致謝。

Answer 1

你提的問題是非常模糊，但這樣的事情可能讓你開始：

select r.*, rh.max_updated, rh.min_updated 
from report as r 
    join (
    select report_fk, 
      min(updated_datetime) as min_updated, 
      max(updated_datetime) as max_updated 
    from report_history 
    group by report_fk 
) as rh on rh.report_fk = r.pk;