Re: Jaw drop: JDBC will let you update rows with the wrong data type (within reason)

JPA - I am a big fan !! However sometimes you need to go below the beauty
of JPA - If your have a legacy ( QS36F ) database or you jys need to do
something more dynamic that realy dont maps into the entity manager ...

Now: auto-cast ... Yes it has improved a lot: now you can even use concat
on int, date , chars etc. happily without thinking about the SQL data types
... I think all the string operations actually now also work on numeric and
data/time/timestamp .. Have not tried it yet though ...

So you post Charles - "Jaw drop: JDBC" - is actually not JDBC .. it is "Jaw
drop: SQL" :)



On Thu, Oct 7, 2021 at 9:06 AM Colin Williams <colinwilliams007@xxxxxxxxx>
wrote:

Do you use JPA? Just asking as eclipselink or hibernate will manage all
this for you and you never have to write jdbc type code or sql again.

On Wed, 6 Oct 2021, 20:58 David Gibbs via JAVA400-L, <
java400-l@xxxxxxxxxxxxxxxxxx> wrote:

Folks:

I just encountered a situation where JDBC allowed me to update rows in a
table where the values did not match the column definition.

As long as you use the setObject method, you can set a numeric column to
a string value and a character column with a numeric value.

The value contents have to match the column definition, but it doesn't
seem to care what the data type being passed in.

For instance:

You create a table as such ...

create table testtab1 (
decfield decimal(8,0),
charfield char(10)
)

... and then run code like this ...

try (
Connection conn = DriverManager.getConnection(url, props);
PreparedStatement stmt = conn.prepareStatement("insert into
dxglib/testtab1 (decfield,charfield) values(?,?)");
) {

stmt.setObject(1, 1);
stmt.setObject(2, "xyz");
stmt.executeUpdate();

stmt.setObject(1, "2");
stmt.setObject(2, 3);
stmt.executeUpdate();

stmt.setObject(1, "A");
stmt.setObject(2, 3);
stmt.executeUpdate();

} catch (Exception e) {
e.printStackTrace();
}

.. the first two updates will work fine, but the 3rd will fail.

david
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