We can get the object definition from DBC.TVM table and from other DBC views.Fine! But, if the request text size exceeds the limits set for the field in the dictionary Table,the object definition is truncated at the ends before storing it into dictionary.The other general method to display the object definition is by using SHOW statement.
Now,I want to understand how SHOW command gets the table definition. Does it query Dictionary table to get the definition? if yes, Which table? else, how does Teradata processes this request i.e.,SHOW [OBJECT][OBJECT NAME];
I have same doubt regarding the HELP [OBJECT] [OBJECTNAME];
The dictionary tables contain all object definitions defined on the database. A SHOW or HELP statement is just like any other SQL statement such as a SELECT for example. It causes the Par$er to read the appropriate dictionary tables to figure out what to do with the SQL statement. In the case of a SHOW it will just builds the output text for the requested object. For a SELECT it will acquire all of the information from the dictionary tables (if not already cached) to build the request, optimize it and build the steps necessary to execute the request. For a SHOW TABLE it will need to access the dictionary tables you mentioned. For a SHOW FUNCTION it will need to access those and some others. So it depends on the type of object the SHOW is for.