Examine the following statement that is used to modify the primary key constraint on the SALES
table:
SQL> ALTER TABLE SALES MODIFY CONSTRAINT pk DISABLE VALIDATE;
Which three statements are true regarding the above command? (Choose three.)
A.
The constraint remains valid.
B.
The index on the constraint is dropped.
C.
It allows the loading of data into the table using SQL *Loader.
D.
New data conforms to the constraint, but existing data is not checked.
E.
It allows the data manipulation on the table using INSERT/UPDATE/DELETE SQL statements.
In order to better handle temporarily constraint violation, the constraints can be specified as a different state. You can be enabled (ENABLE) or disabled (DISABLE) integrity constraints.
If the constraint is enabled, then check the data input or update data in the database. At this time, prohibit the importation does not meet the data constraint rules.
If you disable the constraint, you can enter the data does not comply with the rules in the database.
DISABLE NOVALIDATE is the same as DISABLE.
The constraint is not checked and is not necessarily true.
DISABLE VALIDATE disables the constraint, drops the index on the constraint,
and disallows any modification of the constrained columns.
DISABLE VALIDATE: not allowed to have a column constraints make any modifications. Because if after verification of existing data, and allows unchecked data entry table, there will be inconsistencies. Normally, when you must verify an existing data without modification, and does not require an index to improve performance, you can use this status.
Disable validate
Allows SQL loader and drops the index
Constraint still exists, just not validated
(See below)
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In such situations, the disable validate state
enables you to save space by not having an index. You can then load data from a non-partitioned
table into a partitioned table using the exchange_partition_clause of the
ALTER TABLE statement or using SQL*Loader. All other modifications to the table
(inserts, updates, and deletes) by other SQL statements are disallowed.
If the unique key coincides with the partitioning key of the partitioned table, disabling
the constraint saves overhead and has no detrimental effects. If the unique key does not
coincide with the partitioning key, Oracle performs automatic table scans during the
exchange to validate the constraint, which might offset the benefit of loading without
an index.
D is wrong, the constraint is disabled, and will not validate new data