Hello together,

Despite it is a good idea using SQL in its pure descriptive nature, because it normally leads to generally better performance, one has to be aware of caveats in assuming that things are evaluated in an "intuitive order".

Neither the relatinonal nor the boolean algebra does explicitly defines an evaluation order.

In regard to this article it is assumed that the boolean subexpressions will be evaluated from right to left in an fail-fast-manner. Although this could be implemented like that it does not need to. Thus leading to unportable and/or bad performing queries. Just imagine that the default values for the positional parameters would have been changed to the empty string and the evaluation would be left-to-right. The query will do always a full scan over the possibly huge table with returning unwanted tuples.

Therefore one should never assume the natural order in SQL-Queries as long as These are not guaranteered by the DBS.