insert& update incremental load leads to two rows instead of a updated one

[ioannagr]

Hi, i followed the instructions from Qlik Help to create this Inser and Update (no delete) script like so:

QV_Table:

SQL SELECT PrimaryKey, X, Y FROM DB_TABLE

WHERE ModificationTime >= #$(LastExecTime)#;

Concatenate LOAD PrimaryKey, X, Y FROM File.QVD

WHERE NOT Exists(PrimaryKey);

STORE QV_Table INTO File.QVD;

And for a row i get the old row and also the updated one. Is that correct? 

Why doesn't it only keep the updated row?