Question

Which keyword is used while adding constraint to an existing table to avoid verifying old value within the column?
​

Answer 1

Answer:

Constraints can also be added to tables that have already been created. To add a constraint to an existing table you must use the ALTER TABLE statement. This statement is used to add or delete columns and constraints in an existing table.

Explanation:

Correct me if im wrong:)

Answer 2

Answer:

Use the ALTER TABLE statement to apply a constraint to an existing table to avoid verifying old value within the column. Use this statement to add or remove constraints and columns from an existing table.

Explanation :

• A table's columns can be added, removed, or modified using the SQL ALTER TABLE command.
• The ALTER TABLE command should also be used to add and remove different constraints from an existing table.
• Using the NOVALIDATE keyword, you can surely build a constraint that will validate any newly added or altered records but not older existing data.
• To declare a primary key, foreign key, referential, unique, or check constraint on a new or existing column or on a set of columns, use the ADD CONSTRAINT clause.
• The ALTER TABLE statement includes this chunk of syntax. Notes: Use the MODIFY Clause in place of the NULL and NOT NULL limitations.
• You cannot apply a UNIQUE constraint if you want to maintain your current duplicate entries while enforcing some type of uniqueness for all future entries.
• The value to be put could be compared to the current table values using a trigger on the table, and if it already exists, the insert could be stopped.

• The following is the fundamental syntax for an ALTER TABLE command that adds a New Column to an existing table.

ALTER TABLE table_name ADD column_name datatype;

#SPJ3