In a relational database, a table is classified as a parent table and you want to drop and re create it. How can you do this without damaging or losing data in the child tables?

Introduction / Context:
In relational database design, parent and child tables are linked by foreign key constraints. Sometimes a database administrator needs to drop and re create a parent table, perhaps to change its structure or storage parameters. Doing this incorrectly can break referential integrity or remove constraints needed by child tables. Understanding the correct procedure to modify a parent table while preserving child data and relationships is an important DBA skill and a common interview question.

Given Data / Assumptions:

• There is a parent table with a primary key referenced by foreign keys in one or more child tables.
• You need to drop and re create the parent table, possibly with changed definitions.
• You want to preserve all data and relationships in the child tables.
• The database supports disabling or dropping and re creating foreign key constraints.

Concept / Approach:
Foreign key constraints in child tables depend on the existence of the parent table and its primary key. If you drop the parent table without handling these constraints, the database may prevent the drop or remove the constraints in an uncontrolled way. The safe approach is to temporarily disable or drop the foreign key constraints referencing the parent, then drop and re create the parent table, and finally re enable or re create the foreign key constraints after confirming that the new parent structure is compatible. Throughout this process, child table data is preserved, and referential integrity is restored at the end.

Step-by-Step Solution:
Step 1: Identify all child tables that have foreign key constraints pointing to the parent table you intend to drop.Step 2: Record the definitions of these foreign key constraints, for example by scripting them from the data dictionary or using a database administration tool.Step 3: Temporarily disable or drop the foreign key constraints in the child tables so that they no longer depend on the parent table.Step 4: Drop the parent table and re create it with the required new structure, ensuring that the primary key columns remain compatible with the foreign key definitions.Step 5: Re enable or re create the foreign key constraints on the child tables so that referential integrity is re established without any loss of child data.

Verification / Alternative check:
After performing these steps in a test environment, you can verify success by querying child tables to confirm that rows are still present and that foreign key constraints are active. Attempting to insert inconsistent data, such as a child row referencing a non existent parent, should fail, indicating that referential integrity is enforced again. You can also check the data dictionary or system catalog views to confirm that all constraints have been restored and that the parent table structure matches the expectations of related queries and applications.

Why Other Options Are Wrong:
Option B suggests deleting all child rows first, which destroys valuable data and usually defeats the purpose of preserving relationships. Option C describes shutting down the database and removing data files, which would remove all tables, not just the parent, and is far too destructive. Option D suggests renaming the parent table without updating foreign keys, which would break references and cause runtime errors because constraints would still point to the old object name. None of these approaches preserve child data and referential integrity in a controlled way.

Common Pitfalls:
A common pitfall is failing to capture the exact definitions of foreign key constraints before dropping them, making it difficult to re create them correctly. Another mistake is changing the primary key structure of the parent table without updating foreign keys, leading to mismatched data types or key columns. DBAs should always test such operations in a non production environment, document each step, and maintain scripts for constraint management. Proper planning and verification ensure that structural changes to parent tables do not harm existing child data or application behaviour.

Final Answer:
Correct answer: Temporarily disable or drop the foreign key constraints in child tables, drop and re create the parent table, then re enable or re create the constraints