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Data Based

Just some thoughts of mine

As a concise example of the evils of type coercion I came up with the following:

INSERT INTO t
VALUES (
CAST(2 AS INT),
CAST(2 AS INT));

SELECT
CASE WHEN x + z = 4 THEN '4' ELSE 'NOT 4' END xPLUSz
FROM t;

Result:

xPLUSz
------
NOT 4

It is left as an exercise for the reader to work out what types x and z might be!

Published 26 August 2009 21:02 by David.Portas

Filed under: SQL, Data

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	Luciano Evaristo Guerche (Gorše) said: What about the following CREATE TABLE statement? CREATE TABLE t (x varchar, z varchar); August 27, 2009 14:56
	Erwin Smout said: I thought of CHAR types too. But are you certain that coercions, by and of themselves, are the only source of the problem ? Isn't obtuse operator overloading at least as much responsible here ? October 8, 2010 21:50
	Paul White said: CREATE TABLE t (x BIT NULL, z DATETIME NULL) August 31, 2011 12:12