String or binary data would be truncated: Error not caught by TRY_CAST

Question

The query below...

SELECT YEAR(TRY_CAST(m.MetaValue AS DATE))
FROM MetaData m

...results in this error:

String or binary data w         


        

Answer 1

You get this issue if MetaValue is > 8,000 bytes. It throws an error not caught by the TRY_CAST.

A simple demo of this is below (db <> fiddle)

DECLARE @X NVARCHAR(MAX) = 'X'
SET @X = REPLICATE(@X, 4001)

SELECT TRY_CAST(@X AS DATE)

In general SQL Server can evaluate expressions out of logical processing order causing the potential for this even if all the ones matching the WHERE MetaKey IN (...) condition are short strings (also warned about here).

Guarding the TRY_CAST in an additional CASE expression should resolve things in this case

SELECT CASE WHEN DATALENGTH(m.MetaValue) <8000 THEN YEAR(TRY_CAST(m.MetaValue AS DATE)) END
FROM MetaData m
WHERE m.MetaKey IN (...)