You are debugging a PL/SQL block where you suspect a SELECT INTO statement might return more than one row, but your code is not designed to handle this. You want to add exception handling to catch this scenario and display a warning message specifically. Which of the following EXCEPTION handlers is appropriate for this purpose?

Question

BlackTom AI · Accepted Answer

In this question, we’re focusing on handling a potential scenario where a SELECT INTO in PL/SQL returns more than one row, which the block is not designed to handle.
Option 1 (assumed correct): EXCEPTION WHEN TOO_MANY_ROWS THEN DBMS_OUTPUT.PUT_LINE('Warning: More than one row returned by SELECT INTO. Check query logic.');
This is the appropriate handler for the situation where a SELECT INTO returns more than one row. TOO_MANY_ROWS is raised specifically when the query yields more than one result, so catching this exception and emitting a warning message helps identify the logical issue in the query without crashing the block.
Option 2 (assumed NO_DATA_FOUND): EXCEPTION WHEN NO_DATA_FOUND THEN DBMS_OUTPUT.PUT_LINE('Warning: No data found for the SELECT INTO statement.');
 NO_DATA_FOUND is raised when the query returns zero rows. While this is a valid and important exception to handle in some contexts, it does not address the problem of multiple rows being returned. Therefore, it would not alert you to the intended issue in this scenario.
Option 3 (assumed OTHERS): EXCEPTION WHEN OTHERS THEN DBMS_OUTPUT.PUT_LINE('An unexpected error occurred: ' || SQLERRM); 
Using OTHERS is a catch-all that will trap all exceptions not previously handled. While it can prevent abrupt failures, it is too broad for the specific goal of detecting a too-many-rows condition, and it obscures the precise cause unless you further inspect SQLCODE/SQLERRM. Relying on OTHERS for this targeted issue is not best practice.
Option 4 (assumed DUP_VAL_ON_INDEX): EXCEPTION WHEN DUP_VAL_ON_INDEX THEN DBMS_OUTPUT.PUT_LINE('Warning: Duplicate value on index detected.');
DUP_VAL_ON_INDEX arises when a unique or primary key constraint is violated during an insert, not during a SELECT INTO. This option does not pertain to the scenario of a SELECT INTO returning multiple rows, so it would be inappropriate here.

Summarizing the logic: the problem statement pinpoints a SELECT INTO potentially returning more than one row. The most specific and correct exception for that case is TOO_MANY_ROWS. The NO_DATA_FOUND option addresses no-row results, not multiple rows. OTHERS is too broad and hides the exact issue, and DUP_VAL_ON_INDEX is unrelated to a SELECT INTO’s row-count outcome. Therefore, the targeted and precise choice is the TOO_MANY_ROWS handler.

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