HEIDENHAIN TNC 620 User Manual page 335

9
Accessing tables with SQL commands 9.9
Result set
The selected rows are numbered in ascending order within the
result set, starting from 0. This numbering is referred to as the
index. The index is used for read and write accesses, enabling a
row of the result set to be specifically addressed.
It can often be advantageous to sort the rows in the result set. Do
this by specifying the table column containing the sorting criteria.
Also select ascending or descending order (SQL SELECT ... ORDER
BY ...).
The selected rows that were transferred to the result set are
addressed with the HANDLE. All following SQL commands use the
handle to refer to this "set of selected columns and rows."
When concluding a transaction, the handle is released (SQL
COMMIT... or SQL ROLLBACK...). It is then no longer valid.
You can edit more than one result set at the same time. The SQL
server assigns a new handle for each "Select" command.
"Binding" Q parameters to columns
The NC program does not have direct access to the table entries in
the result set. The data must be transferred in Q parameters. In the
other direction, the data is first prepared in the Q parameters and
then transferred to the result set.
Specify with SQL BIND ... which table columns are mapped to
which Q parameters. The Q parameters are "bound" (assigned) to
the columns. Columns that are not bound to Q parameters are not
included in the read-/write-processes.
If a new table row is generated with SQL INSERT..., the columns
not linked to Q parameters are filled with default values.
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HEIDENHAIN | TNC 620 | Conversational Programming User's Manual | 10/2015