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What is the main use of the SQL LAG function in analytic queries?

easy📝 Conceptual Q1 of 15
SQL - Advanced Window Functions
What is the main use of the SQL LAG function in analytic queries?
ATo join two tables based on a key
BTo calculate the sum of values in a column
CTo filter rows based on a condition
DTo access data from a previous row within the same result set
Step-by-Step Solution
Solution:

  1. Step 1: Understand LAG function

    The LAG function is used to retrieve data from a previous row in the same result set without using a self-join.

  2. Step 2: Compare options

    Options B, C, and D describe other SQL operations unrelated to LAG.

  3. Final Answer:

    To access data from a previous row within the same result set -> Option D

  4. Quick Check:

    LAG accesses previous row data [OK]
Quick Trick: LAG fetches previous row's value in ordered data [OK]
Common Mistakes:
  • Confusing LAG with aggregate functions
  • Thinking LAG filters rows
  • Assuming LAG performs joins

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