69. In Oracle, use the ____________________ command to display the structure of a table.
70. You can change the characteristics of existing columns by using the ____________________ clause of the ALTER
TABLE command.
71. To change a column that currently rejects null values so that it accepts null vlaues, use the ____________________
clause in the ALTER TABLE command.
72. You can delete a table that is no longer needed by using the ____________________ TABLE command.
73. Describe the format for the UPDATE command.
The format for the UPDATE command is the word UPDATE, followed by the name of the table to be
updated. The next portion of the command consists of the word SET, followed by the name of the
column to be updated, an equals sign, and the new value. When necessary, include a WHERE clause to
indicate the row(s) on which the change is to take place.
74. How can you use the COMMIT and ROLLBACK commands to support transactions?
You can use the COMMIT and ROLLBACK commands to support transactions as follows:
Before beginning the updates for a transaction, commit any previous updates by executing the
COMMIT command.
Complete the updates for the transaction. If any update cannot be completed, execute the ROLLBACK
command and discontinue the updates for the current transaction.
If you can complete all updates successfully, execute the COMMIT command after completing the final
update.
75. Describe the format of the ALTER TABLE command to add a new column.