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Databases & SQLQuery Optimization & Execution Plans

24 items

1

Composite Index Column Order Bug

Code Quiz
2

Composite Index Column Ordering and Ranges

Quiz
3

Composite Index Column Order Bug

Code Quiz
4

Composite Index Column Order

Quiz
5

EXPLAIN Plans & Composite Indexes

Slides / Video
6

Composite Indexes & Column Order

Flashcard
7

Partition Pruning Defeated by a Function

Code Quiz
8

Diagnosing a Skewed Hash Join at Scale

Quiz
9

Data Skew and Join Strategy at Scale

Flashcard
10

Execution Plans & Optimization at Scale

Slides / Video
11

Non-SARGable Predicate Kills Index

Code Quiz
12

Diagnosing Slow Plans at Scale

Quiz
13

Execution Plans at Scale

Flashcard
14

Execution Plans at Scale

Slides / Video
15

LEFT JOIN Silently Becomes INNER JOIN

Code Quiz
16

Join Order and Cardinality Estimation

Quiz
17

Non-Sargable Predicate Kills Index Usage

Code Quiz
18

Estimated vs Actual Row Counts

Quiz
19

CTE Materialization and Optimization Fences

Quiz
20

CTE Materialization vs Inlining

Flashcard
21

Complex Joins, CTEs & Perf Reasoning

Slides / Video
22

Query Performance & Execution Plans

Slides / Video
23

Reading a Query Execution Plan

Quiz
24

Indexes and Execution Plans

Flashcard
Flashcard

Composite Indexes & Column Order

How composite index column order and the leftmost-prefix rule determine whether EXPLAIN shows an index seek or a scan.

Question

In a composite index (a, b, c), why does column order matter, and how does EXPLAIN reveal misuse?

Click to reveal answer