hiya
Quote:
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An internal schema is an organization of data according to the technology being used to record it. This includes the terms for components recognized by each kind of data manipulation technology: relational database management system (DBMS) "tables," hierarchical DBMS "segments," object "classes," etc. It also includes the terms for the internal physical storage of data on the computer (cylinder, track, etc.). In the past, the DBMS terms have comprised the logical schema, and the physical storage terms have comprised the physical schema. The internal schema is really two: the logical schema which represents data in terms appropriate to a particular data manipulation approach as usually expressed in a database management system or DBMS (the "designer's view") and the internal schema which is concerned with the physical characteristics of storage on a storage device ("builder's view").Internal schema ( and thus logical schema ) is at level three of the ANSI / SPARC architecture.”
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Since I only know ( a little ) about relational database, I’m going to ask the following question in the context of relational database:
Anyways, the way I understand the above paragraph is that logical schema is actually a level with which administrator directly interacts when he / she is creating new tables, keys etc. I assume this since conceptual level doesn’t know about tables, instead it knows only of objects ( entities ). Point I’m trying to make is that according to above definition of logical level the DDL statements such as:
CREATE TABLE UH ( … )
should operate at logical and not conceptual level, since conceptual level doesn’t know about tables!
Yet, as far as I know if there is clear distinction between conceptual and logical levels, then DDL operates at conceptual and SDL and logical level. That doesn’t make sense!
BTW – I realize that most DBMS don’t have a clear separation between conceptual and logical level
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