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Step 16
3 min read

Selective Projection

Learn to select only the columns you need for better performance.

What is Selective Projection?

SELECT Comparison
SELECT *SELECT columns
More memoryLess memory
Slower networkFaster network
Can break codeStable code
3 rows

Only SELECT the columns you need. Avoid SELECT *.

Example

SELECT Comparison
SELECT *SELECT columns
More memoryLess memory
Slower networkFaster network
Can break codeStable code
3 rows

Bad:

SELECT * FROM products; -- Gets 20 columns

Good:

SELECT name, price FROM products; -- Gets only 2

Why It Matters

SELECT Comparison
SELECT *SELECT columns
More memoryLess memory
Slower networkFaster network
Can break codeStable code
3 rows

Summary

SELECT Comparison
SELECT *SELECT columns
More memoryLess memory
Slower networkFaster network
Can break codeStable code
3 rows
  • Always list columns you need
  • Avoid SELECT * in production
  • Less data = faster queries

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Query Analysis Techniques