I am learning DQL, as I knonw it is a superset of SQL.
There are different kind of RDBMS are present and they are having there own SQL interpretation.
So how DQL handels these diverse RDBMS?
I am learning DQL, as I knonw it is a superset subset of SQL.
There are many Content Server flavours for a specific version dedicated to the supported RDBMS. It just translates the common DQL clause into the corresponding SQL that is expected by the backend database.
Perhaps you might be right, but please clarify me.
If DQL has more clouse than SQL, and the Clauses that work upon the SQL clauses.
So I think It would be superset.
All SQL commands are not valid DQL, then DQL is not a superset of SQL.
DQL is superset of ANSI-SQL
So no restriction with the RDBMS.
Ahmad Sakhi wrote:DQL is superset of ANSI-SQL
Do you know about SQL92 standard specification? It's ANSI, but DQL does not conform even 10% of this standard.
PanfilovAB wrote:Do you know about SQL92 standard specification? It's ANSI, but DQL does not conform even 10% of this standard.
No. Can you give an example, please?
Ahmad Sakhi wrote:PanfilovAB wrote:Do you know about SQL92 standard specification? It's ANSI, but DQL does not conform even 10% of this standard.No. Can you give an example, please?
SQL-92 - Wikipedia, the free encyclopedia
Awesome! You have written keyword "ANSI", but you have no idea what it means.
Well, google being at your fingertip, i don't think anyone would have difficulties finding what an acronym means. But that wasn't the point really. I should have mentioned the keyword 'standard'. It's (or at least it was) actually ANSI-Standard SQL. So, not being a DBA, is SQL-92 considered ANSI-Standard SQL? if so, then DQL has to be adjusted as well in order for the DQL definition to stand corrected. I remember this from a text book looong time ago, and it may not stand valid now with major revision of ANSI-standard?
PanfilovAB wrote:I am learning DQL, as I knonw it is a superset subset of SQL.
So, just to clarify -- for my own benefit as I am a learner too -- when DQL is considered subset of SQL, then every DQL statement has to be a valid SQL statement? is that true?
is SQL-92 considered ANSI-Standard SQL?
Yes, SQL92 is ANSI standard, all mature relational databases do conform it.
DQL has to be adjusted as well in order for the DQL definition to stand corrected.
Actually not. You should not consider DQL as SQL dialect. Yes, some DQL clauses look like SQL clauses, and the most (except VDM) of select clauses are translated directly to SQL (otherwise EMC had no chances to sell documentum), but it is not a SQL.
If I am not mistaken (at least before SQL-92), all ANSI-Standard SQL statements were valid DQLs. Am I mistaken on this?
In any case then what would be proper definition of DQL, for the benefit of the OP?
DQL is an SQL-like language (for the sake of developers, so they don't panic) that gets translated into the underlying RDMBS SQL instructions.
Could you demonstrate concatenation operator in DQL (substring extraction, AFAIK, does not conform SQL92)? Or subquery (scalar, row, and table)?
DQL - Document Query Language. Point.
DELETE and UPDATE statements are not translated directly to SQL.
If those are SQL-92, then you maybe correct, but are they? I am again asking for clarification, for my own benefit. Is it true what was printed that 'all ANSI-Standard SQLs are valid DQLs'? I am not a DBA to know all ANSI-Standard SQL statements so we can see if they truly are. I think we can agree and leave it there, that DQL is just Documentum Query Language, period, with ANSI-Standard being revised. Thanks and appreciate the info.
I can't tell you much about this as my database part is weak. But I can surely direct you in some way which may help clear your understanding.
how does a SQL query work? - Stack Overflow
What's your question/point Ahmad? IMHO, the answer is the last one. They have certain common parts, but neither one is a superset of the other. There are plenty of SQL functions that DQL doesnt support and there are some DQL functions that are specific to Documentum and do not apply to all RDBMS.
Johnny,
the second option is the answer, actually , and pressing the "Cheat" button will reveal the correct answer.
I personally disagree with that answer, but since I didnt write the exam, I guess it doesnt really matter.
I recently came across this, and simply wanted to share.
My understanding of DQL vs SQL is this (And I am not a DBA, so I could be wrong)
ANSI SQL is vendor (MS SQL, Oracle, DB2, etc...) independent. Functions specific to say Oracle, MS SQL, DB2 are not considered as part of ANSI SQL. Similarly, functions specific to DQL are not considered ANSI SQL either. So, based on the multiple choice question, considering #2 is correct, any ANSI SQL statement should be a valid DQL statement, but not vice versa. Again, correct me if I am mistaken, please.
As I stated in my previous post, there are some ANSI SQL functions that DQL does not support. For example, ANSI SQL specifies five types of JOIN : INNER , LEFT OUTER , RIGHT OUTER , FULL OUTER and CROSS. AFAIK, DQL does not support all of these. There are other ANSI SQL items that DQL does not support as well (cant think of them at the moment), which is why I think the last option is "more accurate" answer.
I agree with that.
