Truncate a VARCHAR to specific length in Derby AUT

问题:

How can I truncate a VARCHAR to the table field length AUTOMATICALLY in Derby using SQL?

To be specific:

CREATE TABLE A ( B VARCHAR(2) );
INSERT INTO A B VALUES ('1234');

would throw a SQLException:

A truncation error was encountered trying to shrink VARCHAR '123' to length 2.

Is there a easy way to suppress this exception?

回答1:

No. You should chop it off after checking the meta-data. Or if you don't wanna check the meta-data everytime, then you must keep both your code and database in sync. But thats not a big deal, its a usual practice in validators.

回答2:

You can trim the varchar before inserting it. use the trim function in your insert script/procedure.

I'm not familiar with Derby, but in MSSQL I do exactly the same thing, using trim to avoid truncation error (only where I don't need the full data), it's much more preferable to increase the length of the varchar

回答3:

You can use SUBSTR:

CREATE TABLE A ( B VARCHAR(2) );
INSERT INTO A B VALUES (SUBSTR('1234', 1, 2));

In case you use prepared statements:

INSERT INTO A B VALUES (SUBSTR(?, 1, 2));