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Why is it necessary to alias a subquery in the FROM clause in SQL?

medium📝 Conceptual Q10 of 15
SQL - Subqueries
Why is it necessary to alias a subquery in the FROM clause in SQL?
ABecause aliasing encrypts the subquery result
BBecause the SQL standard requires every derived table to have a name for reference
CBecause aliasing creates a permanent table in the database
DBecause aliasing improves query performance automatically
Step-by-Step Solution
Solution:

  1. Step 1: Understand SQL standard rules

    The SQL standard mandates that every subquery in the FROM clause must have an alias to be referenced in the outer query.

  2. Step 2: Clarify misconceptions

    Aliasing does not affect performance, create permanent tables, or encrypt data.

  3. Final Answer:

    Because the SQL standard requires every derived table to have a name for reference -> Option B

  4. Quick Check:

    Alias is mandatory for derived table naming [OK]
Quick Trick: Alias every derived table to avoid syntax errors [OK]
Common Mistakes:
MISTAKES
  • Thinking alias improves performance
  • Confusing alias with permanent table creation
  • Assuming alias encrypts data

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