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Displaying posts with tag: NULL VALUES (reset)
Jul
22
2013
10 Things in SQL Server Which Don’t Work as Expected
Posted by Lukas Eder on Mon 22 Jul 2013 10:47 UTC
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So far, I have been blogging about curious RDBMS caveats mostly related to Oracle and MySQL databases. Some examples: You never stop learning about Oracle features NOT IN vs. NOT EXISTS vs. LEFT JOIN / IS NULL: MySQL SQL incompatibilities: NOT IN and NULL values MySQL Bad Idea #384 But there are also other databases, … Continue reading 10 Things in SQL Server Which Don’t Work as Expected →

Nov
21
2009
ON DUPLICATE KEY With NULL Validation
Posted by Venu Anuganti on Sat 21 Nov 2009 03:01 UTC
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I am not sure if this is a bug or how MySQL works on validating constraints in association with ON DUPLICATE KEY (late or early checking). For example, consider the following use case (this is irrepective of storage engine and MySQL version): 

      mysql> create table t1(id int not null primary key, val int not null) Engine=MyISAM;
Query OK, 0 rows affected (0.07 sec)
 
mysql> insert into t1 values(10,20);
Query OK, 1 row affected (0.01 sec)
 
mysql> insert into t1 values(20,10);
Query OK, 1 row affected (0.00 sec)
 
mysql> create table t2(id1 int not null primary key, val1 int) Engine=MyISAM;
Query OK, 0 rows affected (0.14 sec)
 
mysql> insert into t2 values(10,NULL);
Query OK, 1 row affected (0.00 sec)
 
mysql> insert into t1(id, val) select id1, val1 from t2 ON DUPLICATE KEY UPDATE val=IF (VALUES(val) IS NULL, val, VALUES(val));
Query OK, 2 rows affected, 1 warning (0.00 sec)
Records: 1  Duplicates: 1  Warnings: …
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