Query generated bij AR : what is 't', why is this ?

After doing a simple AR query


and looking at the actual query with WebLogRoute, I see that the resulting SQL query is :

SELECT * FROM ingredient_categorieen t WHERE t.ingredient_categorie_id=‘40’ LIMIT 1

All of this makes sense to me, except the ‘t’ part, as this is nowhere in my Database…

(there is no prefix, there is no table with name ‘t’, ???)

Why does Yii add this ?

I cannot find any material about this in the Yii-guide / cookbook or forum

Does this mean a performance penalty ?

‘t’ is default table alias (CDbCriteria.alias).