It will refer to the state corresponding to the time you executed COMMIT.This means if you have already used COMMIT 10 times, ROLLBACK will have an effect on the last execution you have performed.Whenever you alter the value of a column referenced by the -- All the employees except the manager of -- department (WORKDEPT) 'E21' have been temporarily reassigned.
After that moment, even if you run the ROLLBACK clause 20 times, you can get to the state of only the last COMMIT.
You cannot restore data to a state corresponding to an earlier COMMIT.
The positioned update statement depends on the cursor and any tables the cursor references.
You can compile a positioned update even if the cursor has not been opened yet.
However, removing the open cursor with the JDBC method invalidates the positioned update.
A CREATE or DROP INDEX statement or an ALTER TABLE statement for the target table of a prepared positioned update invalidates the prepared positioned update statement.
Specifying DEFAULT for the update value sets the value of the column to the default defined for that table.
The DEFAULT literal is the only value which you can directly assign to a generated column.
CREATE TABLE table1 (column1 INT, column2 INT, column3 VARCHAR (100)) INSERT INTO table1 (col1, col2, col3) SELECT 1, 11, 'FIRST' UNION ALL SELECT 11,12, 'SECOND' UNION ALL SELECT 21, 13, 'THIRD' UNION ALL SELECT 31, 14, 'FOURTH' CREATE TABLE table2 (column1 INT, column2 INT, column3 VARCHAR (100)) INSERT INTO table2 (col1, col2, col3) SELECT 1, 21, 'TWO-ONE' UNION ALL SELECT 11, 22, 'TWO-TWO' UNION ALL SELECT 21, 23, 'TWO-THREE' UNION ALL SELECT 31, 24, 'TWO-FOUR' Our requirement is that we have table 2 which has two rows where Col 1 is 21 and 31.
We want to update the value from table 2 to table 1 for the rows where Col 1 is 21 and 31.
Before reading this post you may want to get familiar with our post about SQL INSERT Statement.