Oracle FAQ | Your Portal to the Oracle Knowledge Grid |
Home -> Community -> Usenet -> comp.databases.theory -> Re: sql tables
David Cressey wrote:
> "paul c" <toledobythesea_at_ooyah.ac> wrote in message
> news:EbrPi.13483$Da.2157_at_pd7urf1no...
>
>>(note, I changed the thread subject) >> >>Bob Badour wrote: >> >>>David Cressey wrote: >>>... >>> >>>>An SQL DBMS manipulates tables, not relations or relational variables. >>> >>>Exactly. >> >>I presume David could just as well have said "an SQL DBMS manipulates >>SQL tables". Found (finally) a copy of some draft or other of the SQL >>standard at http://www.contrib.andrew.cmu.edu/~shadow/sql/sql1992.txt . >> >>Not sure how this copy might differ from the official ones, but anyway, >>here's some of what it says in section 4.9 which seems to be about >>"Concepts": >> >> >>>4.9 Tables >>> >>> A table is a multiset of rows. A row is a nonempty sequence of >>> values. Every row of the same table has the same cardinality
>>> contains a value of every column of that table. The i-th value
>>> every row of a table is a value of the i-th column of that
>>> The row is the smallest unit of data that can be inserted into
>>> table and deleted from a table. >> >> >>I'm wondering if there are popular SQL dbms's that follow this. For >>example, do any of them let me "insert", say, two "rows" that would be >>considered the same row if a table were a set of rows rather than a >>multiset of rows, giving, eg.: >> >>TableA: >>ColumnA >>1 >>1 >>
>>Also wondering about "i-th" values in rows. Does the above also mean that >> >>TableB: >>ColumnA ColumnB >>1 2 >> >>is not equal to >> >>TableC: >>ColumnB ColumnA >>2 1 >> >>(all other things being equal)?
No apologies necessary. Received on Thu Oct 11 2007 - 11:21:04 CDT