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IS NULL Operator

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IS NULL Operator

The IS NULL operator is used in SQL to check whether a column has no value (NULL). It helps identify missing, unknown, or undefined data in a database.

📝Syntax
SELECT column_name
FROM table_name
WHERE column_name IS NULL;
is-null-operator.sql
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💡What is IS NULL?
  • 1IS NULL checks for missing values.
  • 2It is used in WHERE clause.
  • 3It detects undefined data.
  • 4It is essential for data validation.
💡Why Use IS NULL?
  • 1To find missing data.
  • 2To validate incomplete records.
  • 3To filter optional fields.
  • 4To improve data quality checks.
💡IS NULL vs = NULL
  • 1IS NULL is correct syntax.
  • 2= NULL does not work in SQL.
  • 3NULL cannot be compared using =.
  • 4Special operator is required.
💡IS NULL with Conditions
  • 1Can be combined with AND / OR.
  • 2Used in complex filtering logic.
  • 3Example: WHERE Email IS NULL AND Status = 1.
  • 4Helps refine data queries.
💡IS NULL vs IS NOT NULL
  • 1IS NULL finds missing values.
  • 2IS NOT NULL finds existing values.
  • 3Both are opposite operations.
  • 4Used for data completeness checks.
💡Benefits of IS NULL
  • 1Detect missing data easily.
  • 2Improves data validation.
  • 3Helps in reporting accuracy.
  • 4Simple and widely supported.
🏢Real-world
  • 1Find users without email addresses.
  • 2Identify missing phone numbers.
  • 3Detect unassigned employees.
  • 4Track incomplete registrations.
  • 5Find null values in reports.
⚠Common Mistakes
  • 1Using = NULL instead of IS NULL.
  • 2Confusing NULL with empty string.
  • 3Using IS NULL on non-nullable fields.
  • 4Ignoring NULL checks in filters.
✅Best Practices
  • 1Always use IS NULL for null checking.
  • 2Validate data to reduce NULL entries.
  • 3Combine with IS NOT NULL when needed.
  • 4Use NULL checks in reporting queries.
✅Quick Summary
  • IS NULL checks missing values.
  • Used in WHERE clause.
  • Cannot use = NULL.
  • Helps find incomplete data.
  • Important for data validation.
🎯Interview Questions
Q1. What does IS NULL do in SQL?
Answer: It checks whether a column has no value.
Q2. Can we use = NULL?
Answer: No, we must use IS NULL.
Q3. What is opposite of IS NULL?
Answer: IS NOT NULL.
Q4. Why do we use IS NULL?
Answer: To find missing or unknown values.
Q5. Can IS NULL be used with AND/OR?
Answer: Yes, it can be combined with other conditions.
❓Quiz

Which operator is used to check NULL values?

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OR OperatorNOT OperatorNULL Values in SQLIS NOT NULL OperatorAliases in SQLAggregate FunctionsWhat is SQL?History of SQLFeatures of SQLWhy Learn SQL?
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