[Solved] Given the following setup:CREATE VIEW v_customer AS SELECT customer_id, customer_name FROM customers;CREATE FUNCTION trg_v_customer_insert() RETURNS trigger AS $ BEGININSERT INTO... | PostgreSQL

PostgreSQL - Triggers in PostgreSQL

Given the following setup:

CREATE VIEW v_customer AS SELECT customer_id, customer_name FROM customers;
CREATE FUNCTION trg_v_customer_insert() RETURNS trigger AS $$ BEGIN
INSERT INTO customers(customer_id, customer_name) VALUES (NEW.customer_id, NEW.customer_name);
RETURN NULL;
END; $$ LANGUAGE plpgsql;
CREATE TRIGGER trg_insert INSTEAD OF INSERT ON v_customer FOR EACH ROW EXECUTE FUNCTION trg_v_customer_insert();

What happens when you execute INSERT INTO v_customer VALUES (101, 'Alice');?

AThe trigger causes an infinite loop and the insert never completes.

BThe insert fails because views cannot be directly modified.

CThe insert adds a row to the view but not to the underlying table.

DA new row with customer_id 101 and customer_name 'Alice' is inserted into the customers table.

Step-by-Step Solution

Solution:

Step 1: Understand the trigger function
The trigger function inserts the NEW row data into the underlying customers table.
Step 2: Trigger execution on insert
When inserting into the view, the INSTEAD OF trigger fires and runs the function, inserting the data into customers.
Step 3: Result of the insert
The insert succeeds by adding the row to the base table, even though the view itself is not physically storing data.
Final Answer:
A new row with customer_id 101 and customer_name 'Alice' is inserted into the customers table. -> Option D
Quick Check:
INSTEAD OF triggers redirect inserts to base tables [OK]

Quick Trick: INSTEAD OF triggers redirect inserts to base tables [OK]

Common Mistakes:

Assuming inserts on views always fail
Thinking the view stores data physically
Expecting the trigger to modify the view instead of the table

Master "Triggers in PostgreSQL" in PostgreSQL

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Given the following setup:

Step 1: Understand the trigger function

Step 2: Trigger execution on insert

Step 3: Result of the insert

Final Answer:

Quick Check:

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