CS TECHIIE | SQL Notes and Solutions
Practical SQL exercise: Tests NULL with IS NULL.
Objective
Tests NULL with IS NULL.
Explanation
Read the statement clause by clause and predict the result before executing it. These examples use common relational SQL; table setup and exact syntax can vary between MySQL, PostgreSQL, SQL Server, Oracle and SQLite.
Safety check
Before running UPDATE or DELETE, run a SELECT with the same WHERE condition. Use a test database and a transaction for changes you need to verify.
Program / SQL Solution
SELECT * FROM students WHERE city IS NULL;Practice and revision
- Run the example and verify the output.
- Change the input and test normal, boundary and invalid cases.
- Write the solution again without looking at the notes.
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