Conversion failed when converting date and/or time from character string. T-Sql - tsql

Question

I have a varchar column in my database called ref003 which stores datetime like the below
2021-04-04 20:01:03
Here, date format is like yyyy-MM-DD
When I execute the below select query I am getting error
SELECT *
FROM FileIndex
WHERE CAST(CONVERT(CHAR(30), CONVERT(DATETIME, Ref003, 105), 101) AS DATE)
BETWEEN CAST(CONVERT(CHAR(10), CONVERT(DATETIME, '01-01-2021', 105), 101) AS DATE)
AND CAST(CONVERT(CHAR(10), CONVERT(DATETIME, '31-12-2021', 105), 101) AS DATE)
And the error is
Msg 241, Level 16, State 1, Line 5 Conversion failed when converting
date and/or time from character string.
What is the problem here and how can I solve this problem?

Answer 1

First, for the conversion you need to convert to VARCHAR, not DATE. Note this expression:
CONVERT(VARCHAR(10), CAST(<your date value> AS DATE), 20)
With that in mind, you can clean your query up like so:
--==== Easily consumable sample data
DECLARE #thetable TABLE (someid INT, thedate DATETIME);
INSERT #thetable
VALUES(1,'2021-04-04 20:01:03'),(2,'2021-06-04 22:01:05'),(1,'2021-04-29 10:31:11');
--==== Solution
SELECT t.*, FormattedDate = fmt.Dt
FROM #thetable AS t
CROSS APPLY (VALUES(CONVERT(VARCHAR(10), CAST(t.thedate AS DATE), 20))) AS fmt(Dt)
WHERE t.thedate BETWEEN '20210401' AND '20210501';
Returns:
someid thedate FormattedDate
----------- ----------------------- -------------
1 2021-04-04 20:01:03.000 2021-04-04
1 2021-04-29 10:31:11.000 2021-04-29