Обсуждение: "DML"
There are a couple of places in the docs where the term "DML" is used,
but it is not defined anywhere. What exactly does it stand for and how
would you define it?
- Thomas
--
Thomas Lockhart lockhart@alumni.caltech.edu
South Pasadena, California
> There are a couple of places in the docs where the term "DML" is used,
> but it is not defined anywhere. What exactly does it stand for and how
> would you define it?
Hmm. Thanks to Don and Jay for a definition. The def ("Data
Manipulation Language") was what I thought, but I find it confusing
that it is used to refer to a subset of "SQL", which also has
"Language" in the acronym.
Would it be acceptable to replace "DML statement" with something like
"data-altering statement"? The phrase shows up in only two places in
our ~700 pages of docs and out of context it doesn't seem to add
value...
--
Thomas Lockhart lockhart@alumni.caltech.edu
South Pasadena, California
At 04:28 PM 6/11/99 +0000, Thomas Lockhart wrote: >Would it be acceptable to replace "DML statement" with something like >"data-altering statement"? The phrase shows up in only two places in >our ~700 pages of docs and out of context it doesn't seem to add >value... It would probably be OK. DML seems to be one of those terms of art, not using it would seem odd to db geeks but they'd understand what you're saying. Using it is incomprehensible to the rest of us. So I'd vote for writing something non-experts can understand. Experts don't need your docs anyway :) - Don Baccus, Portland OR <dhogaza@pacifier.com> Nature photos, on-line guides, and other goodies at http://donb.photo.net
>
>Hmm. Thanks to Don and Jay for a definition. The def ("Data
>Manipulation Language") was what I thought, but I find it confusing
>that it is used to refer to a subset of "SQL", which also has
>"Language" in the acronym.
NO!!!! SQL doesn't stand for *anything*! (Though common practice calls
it Structured Query Language, it was officially called SQL because the
original name of the language was copyrighted.)
SQL is composed of three languages (DML, DDL -- Data Definition Language,
and some TLA that I've forgotten).
(OK, I admit to being persnickity about this.) :)
--
D. Jay Newman ! For the pleasure and the profit it derives
jay@sprucegrove.com ! I arrange things, like furniture, and
http://www.sprucegrove.com/~jay/ ! daffodils, and ...lives. -- Hello Dolly
On Fri, 11 Jun 1999, Don Baccus wrote:
> At 04:28 PM 6/11/99 +0000, Thomas Lockhart wrote:
>
> >Would it be acceptable to replace "DML statement" with something like
> >"data-altering statement"? The phrase shows up in only two places in
> >our ~700 pages of docs and out of context it doesn't seem to add
> >value...
>
> It would probably be OK. DML seems to be one of those terms of
> art, not using it would seem odd to db geeks but they'd understand
> what you're saying. Using it is incomprehensible to the rest of
> us. So I'd vote for writing something non-experts can understand.
I dunno about that one Don. DML and its cousins (DDL and DCL) are
very much in common usage these days. DDL (Data Definintion Language)
would be CREATE TABLE and so on whilst DML is INSERT INTO, UPDATE
and DELETE FROM...DCL (Data Control Language) usually deals with
permissions (GRANT/REVOKE) and often gets lumped in with DDL.
If you have a look at any comprehensive text that tells neophytes
(like yers truly) how to get a handle on SQL the subsets are defined
and referred to by their acronyms (e.g., Groff and Weinberg, 'LAN
Times Guide to SQL' which I keep handy...)
I'm not sure why they originally split up SQL but I know this:
proprietary databases like PROGRESS that claim to `support'
SQL generally don't support *all* the subsets.
PROGRESS, for example, does not support DCL at all. One must use
the `data dictionary', an awkward user interface. It claims to
support DDL but you can't access the tables you make with DDL cmds
via the dictionary. However, DML is fairly well supported, for what
that's worth...
------- North Richmond Community Mental Health Center -------
Anyway, hope I haven't muddied the waters but I wanted to say that
even non-SQL databases use these terms...and almost all SQL textbooks
cover them in detail.
Cheers,
Tom
Thomas Good MIS Coordinator, Senior DBA
Vital Signs: tomg@ { admin | q8 } .nrnet.org Phone:
718-354-5528 Fax: 718-354-5056
/* Member: Computer Professionals For Social Responsibility */
At 01:12 PM 6/11/99 -0400, Thomas Good wrote: >I dunno about that one Don. DML and its cousins (DDL and DCL) are >very much in common usage these days. DDL (Data Definintion Language) >would be CREATE TABLE and so on whilst DML is INSERT INTO, UPDATE >and DELETE FROM...DCL (Data Control Language) usually deals with >permissions (GRANT/REVOKE) and often gets lumped in with DDL. >If you have a look at any comprehensive text that tells neophytes >(like yers truly) how to get a handle on SQL... Hmmm...it appears "The Practical SQL Handbook" gets it wrong, then, as it lumps "select" with data modification statements when it makes its breakdown between DML, data definition, and what they call data administration (clearly they mean the same things as your DCL definition, i.e. grant/revoke type stuff). And the AOLServer guys get it right as they talk about "ns_db dml" working on insert/update/delete and "also data definition" statements, i.e. they recognize the difference in their documentation. OK, in the DML, DCL, and DDL decomposition of things, just what *is* a select statement? You've given a simple definition of the decomposition, why not bottle it and pour it into the docs? ... >PROGRESS, for example, does not support DCL at all. One must use >the `data dictionary', an awkward user interface. Barf > It claims to >support DDL but you can't access the tables you make with DDL cmds >via the dictionary. And Codds hasn't struck them dead with lightning? :) - Don Baccus, Portland OR <dhogaza@pacifier.com> Nature photos, on-line guides, and other goodies at http://donb.photo.net
On Fri, 11 Jun 1999, Don Baccus wrote:
> Hmmm...it appears "The Practical SQL Handbook" gets it wrong,
> then, as it lumps "select" with data modification statements
> when it makes its breakdown between DML, data definition,
> and what they call data administration (clearly they mean
> the same things as your DCL definition, i.e. grant/revoke
> type stuff).
>
> And the AOLServer guys get it right as they talk about
> "ns_db dml" working on insert/update/delete and "also
> data definition" statements, i.e. they recognize the
> difference in their documentation.
>
> OK, in the DML, DCL, and DDL decomposition of things, just what
> *is* a select statement?
Hee hee...according to Guy Harrison who wrote 'Oracle SQL High
Performance Tuning' (a great book) SELECT is NOT part of DML.
It is a QUERY.
Harrison separates SELECT from DML because it does not alter data.
Is this getting murkier or do I really need some coffee?
> You've given a simple definition of the decomposition, why
> not bottle it and pour it into the docs?
I would give it a try, if Thomas wanted it...usually tho I sit back
and try to learn from following this list. Anyway the two books that
I've come to rely on are literally on my coffee table at home, so
maybe tonight I'll have a pint and try to write up a coherent def.
Tom
------- North Richmond Community Mental Health Center -------
Thomas Good MIS Coordinator
Vital Signs: tomg@ { admin | q8 } .nrnet.org Phone:
718-354-5528 Fax: 718-354-5056
/* Member: Computer Professionals For Social Responsibility */
At 01:36 PM 6/11/99 -0400, Thomas Good wrote: >Hee hee...according to Guy Harrison who wrote 'Oracle SQL High >Performance Tuning' (a great book) SELECT is NOT part of DML. >It is a QUERY. >Harrison separates SELECT from DML because it does not alter data. >Is this getting murkier or do I really need some coffee? Murkier :) OK, so SQL can be decomposed into: queries, DML, DDL, DCL. The queries are ... DQL? :) > Anyway the two books that >I've come to rely on are literally on my coffee table at home, so >maybe tonight I'll have a pint .... Taking my "bottle and pour it" advice literally, I see! - Don Baccus, Portland OR <dhogaza@pacifier.com> Nature photos, on-line guides, and other goodies at http://donb.photo.net
Thus spake Thomas Good
> I'm not sure why they originally split up SQL but I know this:
Actually, I think it was the other way around. The term SQL didn't
come into use until DDL, DML and DCL had been in common use. I'm
pretty sure Date didn't mention SQL in his original paper.
--
D'Arcy J.M. Cain <darcy@{druid|vex}.net> | Democracy is three wolves
http://www.druid.net/darcy/ | and a sheep voting on
+1 416 424 2871 (DoD#0082) (eNTP) | what's for dinner.
Thus spake D'Arcy J.M. Cain
> Thus spake Thomas Good
> > I'm not sure why they originally split up SQL but I know this:
>
> Actually, I think it was the other way around. The term SQL didn't
> come into use until DDL, DML and DCL had been in common use. I'm
> pretty sure Date didn't mention SQL in his original paper.
Oops. That would be E.F. Codd, not Chris Date.
--
D'Arcy J.M. Cain <darcy@{druid|vex}.net> | Democracy is three wolves
http://www.druid.net/darcy/ | and a sheep voting on
+1 416 424 2871 (DoD#0082) (eNTP) | what's for dinner.
Thomas Lockhart wrote: > > There are a couple of places in the docs where the term "DML" is used, > but it is not defined anywhere. What exactly does it stand for and how > would you define it? I used it for SELECT, INSERT, DELETE, UPDATE, FETCH and COPY_TO statements. Seems that I was wrong using "DML" for all of them. They are statements for data management and querying. Server computes snapshot only for them. Anytime when I used "DML" in docs it was related to this, i.e. to the time of snapshot calculation. Vadim
Thomas Good wrote: > > > OK, in the DML, DCL, and DDL decomposition of things, just what > > *is* a select statement? > > Hee hee...according to Guy Harrison who wrote 'Oracle SQL High > Performance Tuning' (a great book) SELECT is NOT part of DML. > > It is a QUERY. > Harrison separates SELECT from DML because it does not alter data. But what would you call yer query when the tables have rules/triggers attached that do alter data ? A DML-savvy QUERY ;) BTW, where do all the triggers and rules fall anyway, or ar they a different subset - maybe Data Behaviour Language (DBL) > Is this getting murkier or do I really need some coffee? Maybe next we should try to divide english into sublanguages ?English for Order Giving - EOGEnglish for Describing Things- EDTEnglisg for Discussing SQL Sublanguages - EDSQLL ------------------ Hannu
Thomas Lockhart wrote: > > There are a couple of places in the docs where the term "DML" is used, > but it is not defined anywhere. What exactly does it stand for and how > would you define it? I used it for SELECT, INSERT, DELETE, UPDATE, FETCH and COPY_TO statements. Seems that I was wrong using "DML" for all of them. They are statements for data management and querying. Server computes snapshot only for them. Anytime when I used "DML" in docs it was related to this, i.e. to the time of snapshot calculation. Vadim
Thomas Good wrote: > > > OK, in the DML, DCL, and DDL decomposition of things, just what > > *is* a select statement? > > Hee hee...according to Guy Harrison who wrote 'Oracle SQL High > Performance Tuning' (a great book) SELECT is NOT part of DML. > > It is a QUERY. > Harrison separates SELECT from DML because it does not alter data. But what would you call yer query when the tables have rules/triggers attached that do alter data ? A DML-savvy QUERY ;) BTW, where do all the triggers and rules fall anyway, or ar they a different subset - maybe Data Behaviour Language (DBL) > Is this getting murkier or do I really need some coffee? Maybe next we should try to divide english into sublanguages ?English for Order Giving - EOGEnglish for Describing Things- EDTEnglisg for Discussing SQL Sublanguages - EDSQLL ------------------ Hannu
On 12-Jun-99 Hannu Krosing wrote:
>
> Maybe next we should try to divide english into sublanguages ?
> English for Order Giving - EOG
> English for Describing Things - EDT
> Englisg for Discussing SQL Sublanguages - EDSQLL
And don't forget my favorite:
English for Confusing Things - ECT
not to be confused with it's counterpart:
English That Confuses - ETC
Vince.
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