SQL - Table Constraints
Given the table employees with columns id INT PRIMARY KEY and name VARCHAR(100) NOT NULL, what happens when you run this query?
INSERT INTO employees (id, name) VALUES (1, NULL);
Given the table employees with columns id INT PRIMARY KEY and name VARCHAR(100) NOT NULL, what happens when you run this query?
medium📝 query result Q13 of 15
Step-by-Step Solution
Solution:
Step 1: Understand NOT NULL behavior on insert
NOT NULL means the column cannot accept NULL values during insert or update.Step 2: Analyze the insert statement
The query tries to insert NULL into the name column, violating the NOT NULL constraint, causing an error.Final Answer:
The query fails with an error due to NOT NULL constraint. -> Option AQuick Check:
NOT NULL rejects NULL inserts [OK]
Quick Trick: Inserting NULL into NOT NULL column causes error [OK]
Common Mistakes:
MISTAKES- Assuming NULL is converted to empty string
- Thinking the row inserts ignoring NULL
- Confusing NOT NULL with default values
Master "Table Constraints" in SQL
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