动态声明当前月份的开始/结束日期

Question

I have a pretty basic query that I run monthly. Every month I have to manually change the query to fit the current month start and end date. I've tried using some of the examples from previous answers but can't seem the make it work. Notably because I am trying to include the entire last day of the month, as shown by my 23:59:59 parameter. What is the best way to accomplish this?

SELECT *
FROM WorkOrder
where active = 1 and
WorkOrderStatusId in (6,8) AND
dateCreated >= '5/1/2017' and
dateCreated <= '5/31/2017 23:59:59'

Answer 1

what you can actually do is get the month and year

SELECT *
FROM WorkOrder
where active = 1 and
WorkOrderStatusId in (6,8) AND
year(dateCreated) = 2017
month(dateCreated) = 5  

Answer 2

Three things:

First: dates look like 2017-05-01 not 5/1/2017 in most DBMS representations.

Second: you want this sort of expression (note the < ) to make sure you get all rows. That's a better approach than the 23:59:59 stuff.

where  dateCreated >= '2017-05-01'
  and  dateCreated <  '2017-06-01'

Third, you probably want a way of saying

 where dateCreated >= first_day_of_last_month
   and dateCreated <  first_day_of_this_month

in a way where you don't have to change the query every month.

This works differently in different makes and models of database server. You didn't tell us which one you're using, so...

In MS SQL Server, DATEADD(DAY, 1-DATEPART(DAY, GETDATE()), GETDATE()) gives you the first of the present month, so

where dateCreate >= 
         DATEADD(MONTH, -1, DATEADD(DAY, 1-DATEPART(DAY, GETDATE()), GETDATE()))
  and dateCreate < 
         DATEADD(DAY, 1-DATEPART(DAY, GETDATE()), GETDATE())

In MySQL DATE_FORMAT(CURDATE(), '%Y-%m-01') gives you midnight on the first day of the present month, so this where clause gets last month's rows.

where dateCreated >= DATE_FORMAT(CURDATE(), '%Y-%m-01') - INTERVAL 1 MONTH
  and dateCreated <  DATE_FORMAT(CURDATE(), '%Y-%m-01')

In Oracle (cue if I were a rich man from Fiddler on the Roof ) TRUNC(SYSDATE, 'MM') gives you the first of the month, so this gets last month's rows.

where dateCreate >= ADD_MONTHS(-1, TRUNC(SYSDATE, 'MM'))
  and dateCreate <  TRUNC(SYSDATE, 'MM')