[Solved] You have a table orders with columns order_id INT PRIMARY KEY, customer_id INT NOT NULL, and order_date DATE NOT NULL.... Which is the correct way to add this column? | SQL

SQL - Table Constraints

You have a table orders with columns order_id INT PRIMARY KEY, customer_id INT NOT NULL, and order_date DATE NOT NULL. You want to add a new column status that must always have a value and defaults to 'pending'. Which is the correct way to add this column?

AALTER TABLE orders ADD COLUMN status VARCHAR(20) NOT NULL DEFAULT 'pending';

BALTER TABLE orders ADD COLUMN status VARCHAR(20) DEFAULT 'pending';

CALTER TABLE orders ADD COLUMN status VARCHAR(20) NOT NULL;

DALTER TABLE orders ADD COLUMN status VARCHAR(20);

Step-by-Step Solution

Solution:

Step 1: Understand NOT NULL with default value
Adding a NOT NULL column requires a default value to avoid errors on existing rows.
Step 2: Analyze each ALTER statement
ALTER TABLE orders ADD COLUMN status VARCHAR(20) NOT NULL DEFAULT 'pending'; adds status with NOT NULL and default 'pending', so existing rows get this value. Others miss NOT NULL or default.
Final Answer:
ALTER with NOT NULL and DEFAULT 'pending' is correct. -> Option A
Quick Check:
NOT NULL columns need default when added to existing table [OK]

Quick Trick: Add NOT NULL column with DEFAULT to avoid errors [OK]

Common Mistakes:

MISTAKES

Adding NOT NULL column without default
Assuming default alone enforces NOT NULL
Omitting NOT NULL when required

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Which is the correct way to add this column?

Step 1: Understand NOT NULL with default value

Step 2: Analyze each ALTER statement

Final Answer:

Quick Check:

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