>>To what authorities do you attribute the statement, "SQL is a bad implementation of the relational model"?
>
>I think you will have read DATE: "An intruduction to modern database systems" (or something). Date here describes perfectly why SQL is a bad implementation. Just recently I've read somewhere that even oracle is only a 60% implementation of the relational model. In addition I read some hardcode DB oriented magazines in which the writers do state the same. Too me this is NOT an opinion but a FACT.

Walter,

There is no product on the market that meets Codd's rules completely. Some meet more of them than others and xBase is somewhere at the bottom of the list on this point.

>Though it's record oriented, we could skip this part and work set-oriented: this is also possible.

Codd's whole point is that a relational product will not have any way to access the data other than the relational way. If there is another way then the product is not relational.

>We don't have to use record pointers, nor the commands which affect the current record, We could also use SQL commands.


No, you don't.

>So much for your generated primary keys :), yes it's true, but if you look at my concept, it isn't hard to automate the process and let the computer determine the structured hierarchy by specifying a limited SQL query (no group by and having clauses), though it capabilities might reach further. Maybe this wish could also being described as a FILTERED SQL resultset which is editable, and the indexes are available (both implicitly and explicitly). This FILTERED SQL resultset also must be available when joins are used.

Generated primary keys have nothing to do with what I am saying. The use of a generated PK has no effect of the relationalness of a system other than if the system requires that I generate the key value then it is less relational. If i specify that this field is the primary key and give it a unique value for me, then it is relational.

>But we can use the relational approach, can we ?

Codd's point in his definition, again, is that there is no other way. The relational approach is the only way to access the data.

>To my knowledge SQL was invented by IBM (though i don't know if E.F. codd did help with this implementation). If he would have much to say about the implementation, SQL would not be as worse as it is today... Or Codd and DATE have a huge difference in opinion up here, which i think is highly unlikely.

Relational database theory and SQL were both invented by E. F. Codd while he was working for IBM in the 70's.

I've read Chris Date and he often disagrees with his mentor (Codd).