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From Jean-Yves Linet <jy.li...@gmail.com>
Subject Re: Understanding an UPDATE
Date Tue, 06 Mar 2012 06:56:52 GMT
You don't have where clause in your update, so all rows of t1 are updated.
And as you have no row in t2 with id=1, the select return a null value.

Le 6 mars 2012 02:19, TXVanguard <brett.denner@lmco.com> a écrit :

>
> When I run the following SQL statements in JavaDB:
>
> ================================================
>
> drop table t1;
> drop table t2;
>
> create table t1 ( TXT1 varchar(6), ID integer );
>
> create table t2 ( ID integer, TXT2 varchar(12));
>
> insert into t1 (TXT1,id) values ('ONE',1);
> insert into t1 (TXT1,id) values ('TWO',2);
>
> insert into t2 (id,TXT2) values (2,'TWO');
> insert into t2 (id,TXT2) values (3,'THREE');
>
> UPDATE t1 SET TXT1 = (select (TXT2) FROM t2 WHERE (t2.ID = t1.ID));
>
> =================================================
>
> then, table t1 has the following values:
>
>            VAL1      ID
> ROW 1: <NULL>      1
> ROW 2: 'TWO'         2
>
> Why is the value of column VAL1 in the first row set to <NULL> by the
> update
> statement?
> --
> View this message in context:
> http://old.nabble.com/Understanding-an-UPDATE-tp33448196p33448196.html
> Sent from the Apache Derby Users mailing list archive at Nabble.com.
>
>

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