Fetch a row from the result-set of Statement. Statement
must be created with odbc_prepare/5
using the option fetch(fetch) and be executed using odbc_execute/2. Row
is unified to the fetched row or the atom end_of_file7This
atom was selected to emphasise the similarity to read.
after the end of the data is reached. Calling odbc_fetch/2
after all data is retrieved causes a permission-error exception. Option
is one of:
- next
- Fetch the next row.
- prior
- Fetch the result-set going backwards.
- first
- Fetch the first row.
- last
- Fetch the last row.
- absolute(Offset)
- Fetch absolute numbered row. Rows count from one.
- relative(Offset)
- Fetch relative to the current row.
relative(1) is the same
as next, except that the first row extracted is row 2.
- bookmark(Offset)
- Reserved. Bookmarks are not yet supported in this interface.
In many cases, depending on the driver and RDBMS, the cursor-type
must be changed using odbc_set_connection/2
for anything different from next to work.
Here is example code each time skipping a row from a table‘test’holding
a single column of integers that represent the row-number. This test was
executed using unixODBC and MySQL on SuSE Linux.
fetch(Options) :-
odbc_set_connection(test, cursor_type(static)),
odbc_prepare(test,
'select (testval) from test',
[],
Statement,
[ fetch(fetch)
]),
odbc_execute(Statement, []),
fetch(Statement, Options).
fetch(Statement, Options) :-
odbc_fetch(Statement, Row, Options),
( Row == end_of_file
-> true
; writeln(Row),
fetch(Statement, Options)
).
