Dynamic Case Expression Based on Dates - sql

Question

I have a SQL query that has multiple conditions that will change the WHERE clause. I have three case expressions that dynamically update this WHERE clause. The last two case expressions are working well. However, the first one is more dynamic than the last two and I am having issues with it.
Here is the portion of the table that is applicable to this exercise
(Image of Table)
I need it to work as follows:
When my variable #selection = 1, I need it to sort my return based on two dates being passed in.
When my variable #selection = {any other int}, I need it to return all dates.
Query with Description
...
WHERE
{Start Date} = (case when #selection = 1 then {return all values where Start Date is between two dates that are passed in} else {return all Start Dates})
...
Entire Query
DECLARE #selection integer ;
DECLARE #items integer ;
DECLARE #washTypes integer ;
SET #selection = {Root Container.Selection Group.Selection Checkbox.controlValue} ;
SET #items = {Root Container.Items Group.Items Checkbox.controlValue} ;
SET #washTypes = {Root Container.Types of Wash Group.Wash Types Checkbox.controlValue} ;
SELECT
RAW_CIP_records_ndx as 'Index',
start as 'Start',
stop as 'End',
total_duration as 'Total Duration',
item as 'Item',
wash_type as 'Type of Wash',
operator as 'CIP Operator',
program_complete as 'Program Fully Completed?'
FROM RAW_CIP_records
WHERE
start = (case when #selection = 1 then (BETWEEN '{Root Container.Start Date.formattedDate}' and '{Root Container.End Date.formattedDate}') else start end)
and
item = (case when #items = 0 then 'Receiving Bay 1' when #items = 1 then 'Receiving Bay 2' when #items = 2 then 'Receiving Bay 3' else item end)
and
wash_type = (case when #washTypes = 0 then 'Regular' when #washTypes = 1 then 'Sanitize' when #washTypes = 2 then 'Acid' else wash_type end)
I can get a simple WHERE clause to work with these two dates and the BETWEEN function. However, I can't figure out how to pass all of this into a CASE expression.

Answer 1

You could do it a WHERE condition in one query
WHERE (
#selection = 1 AND (start BETWEEN #startDate and #endDate)
OR #selection <> 1
)
But I would suggest you are better off with two separate queries as it will be more likely to use an index.
IF #selection = 1
SELECT ...
ELSE
SELECT ...

Answer 2

Maybe something like this:
WHERE
1 = (case when #selection = 1 then
case when start BETWEEN '{Root Container.Start Date.formattedDate}' and '{Root Container.End Date.formattedDate}' then 1 else 0 end
else 1
end)
and
item = ...
Warning: this will most likely not make use of any indexes, so only use if performance is acceptable in your case.