Varchar date to datetime sql - sql

Question

I have a varchar date format of 01012018, I need to convert this to a date in a SQL Server view:
CONVERT(VARCHAR(50), CONVERT(DATE, [Date], 103), 103)
I have tried the above with no joy.
Please help

Answer 1

SQL Server can be a bit cumbersome when parsing dates that are not one of the "built-in" ones. You can use parse()/try_parse(), but that is a relatively new function.
In your case, it is pretty simple to construct the date value directly:
select convert(date, concat(right(ddmmyyyy, 4), substring(ddmmyyyy, 3, 2), left(ddmmyyyy, 2)))
from (values ('01012018')) v(ddmmyyyy)

Answer 2

There is no style ddMMyyyy in the CONVERT Date and Time Styles, but there is a dd/MM/yyyy, so you could inject these characters in and convert:
SELECT TRY_CONVERT(date, STUFF(STUFF(v.ddmmyyyy, 5, 0, '/'), 3, 0, '/'), 103)
FROM (VALUES ('01012018')) v (ddmmyyyy);
I've also used TRY_CONVERT incase you have some other "bad" values (perhaps '01312019'). These will return NULL when the varchar represents an invalid date.

Answer 3

Use CONVERT() as
DECLARE #Var VARCHAR(10) = '01012018'
SELECT CONVERT(DATE,
CONCAT( RIGHT(#Var, 4),
SUBSTRING(#Var, 3, 2),
LEFT(#Var, 2)
)
)
Demo
Finally, I would recommend ALTERing your table (which is the right solution) and change the data type of your column to DATE data type.
CREATE TABLE T(
MyCol VARCHAR(10)
);
INSERT INTO T(MyCol) VALUES
('01012018'),
('01022018'),
('01032018'),
('WrongData');
SELECT MyCol
FROM T;
UPDATE T
SET MyCol = TRY_CONVERT(DATE,
CONCAT( RIGHT(MyCol, 4),
SUBSTRING(MyCol, 3, 2),
LEFT(MyCol, 2)
)
);
ALTER TABLE T
ALTER COLUMN MyCol DATE;
SELECT MyCol
FROM T;
Second Demo