How do I Join two SQL tables on Multiple date columns

Question

My first table is Called Date_Table this has all the days of the year dating back to January 2020 and goes all the way to 31 Decemeber 2030.The data looks like this:

Date	Day
01/01/2020 00:00	Wed
02/01/2020 00:00	Thur

My second table Sales_Table consists of sales stages, each stage has a date assigned when it reaches the stage. Here is what my data looks like:

Sale_ID	Enquiry	App Rec	App Passed	Sale Completed
1	01/01/2020 00:00	02/01/2020 00:00	03/01/2020 00:00	05/01/2020 00:00
2	02/01/2020 00:00	03/01/2020 00:00	03/01/2020 00:00	05/01/2020 00:00

My query is this so far:

SELECT COUNT(CASE WHEN [Enquiry] IS NOT NULL THEN 1
 END) AS [Total Enquiries],
      COUNT(CASE WHEN [App Rec] IS NOT NULL THEN 1
 END) AS [Apps Received],
      COUNT(CASE WHEN [App Passed] IS NOT NULL THEN 1
 END) AS [Apps Passed],
      COUNT(CASE WHEN [Sale Completed] IS NOT NULL THEN 1
 END) AS [Completed Sales]
FROM [Date_Table]
      LEFT JOIN [Sales_Table] ON [Date] Between [Enquiry] AND [App Rec] GROUP BY [Date]

This seems to work fine for the first 2 dates but if i add another AND statement in the join I get a parsing of SQL query failed error.

The end report would be a table like this:

Date	Enquiry	App Rec	App Passed	Sale Completed
01/01/2020 00:00	3	6	4	2
02/01/2020 00:00	5	1	11	4

I tried to add all the dates fields to the left join using BETWEEN and AND Like this: LEFT JOIN [Sales_Table] ON [Date] Between [Enquiry] AND [App Rec] AND [App Passed] AND [Sale Completed]

This just gave me a parsing error

Answer 1

See example

with t as(
select 'Enquiry'event,Enquiry as dt
from Sales_Table
union all
select 'App_Rec',App_Rec
from Sales_Table
union all
select 'App_Passed',App_Passed
from Sales_Table
union all
select 'Sale_Completed',Sale_Completed
from Sales_Table
)
,totals as(
select dt
   ,sum(case when event='Enquiry' then 1 else 0 end)Enquiry
   ,sum(case when event='App_Rec' then 1 else 0 end)App_Rec
   ,sum(case when event='App_Passed' then 1 else 0 end)App_Passed
   ,sum(case when event='Sale_Completed' then 1 else 0 end)Sale_Completed
from t
group by dt
)
select *
from Date_Table d
left join totals t on t.dt=d.date

Output is

Date	Day	dt	Enquiry	App_Rec	App_Passed	Sale_Completed
2020-01-01	Wedn	2020-01-01	1	0	0	0
2020-01-02	Thur	2020-01-02	1	1	0	0
2020-01-03	Frid	2020-01-03	0	1	2	0
2020-01-04	Satu	null	null	null	null	null
2020-01-05	Sund	2020-01-05	0	0	0	2

with test data

create table Date_table(Date date,  Day varchar(10));
insert into Date_Table ([date]) values 
 ('2020-01-01')
,('2020-01-02')
,('2020-01-03')
,('2020-01-04')
,('2020-01-05')
;
update Date_Table
  set [Day]=left(datename(dw,[date]),4)
;
create table Sales_Table (Sale_ID int,Enquiry date,App_Rec date, App_Passed date, Sale_Completed date);
insert into Sales_Table values
 (1,'2020-01-01','2020-01-02','2020-01-03','2020-01-05')
,(2,'2020-01-02','2020-01-03','2020-01-03','2020-01-05')
;

Fiddle