HEIDENHAIN TNC 620 E, Руководство пользователя

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Programming Q Parameters | Accessing tables with SQL commands
10
HEIDENHAIN | TNC 620 | Conversational Programming User's Manual | 10/2017
437
SQL ROLLBACK
Example
11 SQL BIND Q881 "Tab_Example.Meas_No"
12 SQL BIND Q882 "Tab_Example.Meas_X"
13 SQL BIND Q883 "Tab_Example.Meas_Y"
14 SQL BIND Q884 "Tab_Example.Meas_Z"
. . .
20 SQL Q5 "SELECT Meas_no,Meas_X,Meas_Y, Meas_Z FROM
Tab_Example"
. . .
30 SQL FETCH Q1 HANDLE Q5 INDEX+Q2
. . .
50 SQL ROLLBACK Q1 HANDLE Q5
SQL ROLLBACK
discards all of the changes and additions of a
transaction. The transaction is defined via the
HANDLE
to be
specified.
The function of the SQL command
SQL ROLLBACK
depends on the
INDEX
:
Without
INDEX
:
All changes and additions to the transaction are discarded
A lock that was set with
SELECT...FOR UPDATE
is canceled.
The transaction is concluded (the
HANDLE
loses its validity)
With
INDEX
:
Only the indexed row remains in the
result set
(all other
rows are removed)
Any changes and additions made in the rows that are not
specified are discarded
A lock that has been set with
SELECT...FOR UPDATE
remains only for indexed row (all other locks are canceled)
The specified (indexed) row becomes the new row 0 of the
result-set
The transaction is not concluded (the
HANDLE
keeps its
validity)
It is necessary to later concluded the transaction using
SQL
ROLLBACK
or
SQL COMMIT
Parameter No. for result
(return value for the
control):
0
successful transaction
1
successful transaction
Database: SQL access ID
: Define Q parameters
for the
HANDLE
(for identifying the transaction)
Database: Index to SQL result
: Row that
remains in the
result set
Program the row number directly
Program the Q parameter containing the
index