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CREATE INDEX

Create a single-column index.

CREATE INDEX

With CREATE INDEX you add an index to a column. Queries on that column speed up.

CREATE INDEX idx_email ON customers (email);

Index on the email column.

The index idx_email is created.

CREATE INDEX — details

The index name must be unique. Indexes go on frequently queried columns.

A naming pattern like idx_table_column makes it easier later to tell what each index belongs to (e.g. idx_customers_email).

Practice CREATE INDEX

Add an index on the email column of customers.

Starter code

query.sql
-- email index
CREATE INDEX idx_email

Sample solution

query.sql
CREATE INDEX idx_email ON customers (email);

Expected output

İndeks oluşturuldu

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Add ON

Question 
CREATE INDEX idx_email ____ customers (email);
Answer 
CREATE INDEX idx_email ON customers (email);

Explanation: ON says which table and column the index is built on.

2 How must an index name be?

  • Unique Correct answer
  • Empty
  • The same
  • Random

Explanation: The index name must be unique.

3 CREATE INDEX: match the terms

Term Meaning
CREATE INDEX create
ON on
column column
speed boost

All lessons in Intermediate

1 INNER JOIN in depth

  1. INNER JOIN logic
  2. Choosing the join column
  3. Three-table INNER JOIN
  4. Self JOIN
  5. Filtering joins
  6. Summary - INNER JOIN

2 LEFT and RIGHT JOIN

  1. LEFT JOIN
  2. RIGHT JOIN
  3. Unmatched rows
  4. JOINs with NULL
  5. LEFT vs RIGHT
  6. Summary - LEFT and RIGHT JOIN

3 FULL and CROSS JOIN

  1. FULL OUTER JOIN
  2. CROSS JOIN
  3. When to CROSS JOIN
  4. Comma JOIN
  5. Choosing a JOIN type
  6. Summary - FULL and CROSS JOIN

4 Project: Library database

  1. Library design
  2. Books and authors
  3. List loans with LEFT JOIN
  4. Find overdue loans
  5. Member summary

5 GROUP BY

  1. What is GROUP BY?
  2. Single-column grouping
  3. Multi-column grouping
  4. GROUP BY with aggregates
  5. Ordering grouped results
  6. Summary - GROUP BY

6 HAVING

  1. What is HAVING?
  2. HAVING vs WHERE
  3. HAVING with aggregates
  4. Multiple conditions
  5. HAVING with aliases
  6. Summary - HAVING

7 Aggregate functions

  1. COUNT
  2. SUM
  3. AVG
  4. MIN and MAX
  5. NULL and aggregates
  6. Summary - Aggregates

8 Project: Sales report

  1. Sales design
  2. Daily revenue
  3. Best sellers
  4. Customer segments
  5. Low performers

9 Subquery

  1. What is a subquery?
  2. Scalar subquery
  3. Subquery with IN
  4. ANY and ALL
  5. Correlated subquery
  6. Summary - Subquery

10 EXISTS

  1. What is EXISTS?
  2. NOT EXISTS
  3. EXISTS vs IN
  4. EXISTS performance
  5. Multiple EXISTS
  6. Summary - EXISTS

11 UNION and INTERSECT

  1. UNION
  2. UNION ALL
  3. INTERSECT
  4. EXCEPT
  5. Set rules
  6. Summary - UNION and INTERSECT

12 CASE

  1. What is CASE?
  2. Searched CASE
  3. Simple CASE
  4. The ELSE branch
  5. CASE with aggregates
  6. Summary - CASE

13 VIEW

  1. What is a VIEW?
  2. CREATE VIEW
  3. Querying a VIEW
  4. DROP VIEW
  5. Updatable VIEWs
  6. Summary - VIEW

14 INDEX basics

  1. What is an INDEX?
  2. CREATE INDEX
  3. Composite INDEX
  4. DROP INDEX
  5. When to index
  6. Summary - INDEX

15 Project: Blog database

  1. Blog design
  2. Post list
  3. Tag search
  4. Author stats
  5. Search index

16 Normalization

  1. What is normalization?
  2. First normal form
  3. Second normal form
  4. Third normal form
  5. BCNF
  6. Summary - Normalization

17 Data integrity

  1. What is integrity?
  2. Entity integrity
  3. Referential integrity
  4. Domain integrity
  5. Integrity with triggers
  6. Summary - Data integrity

18 Transaction basics

  1. What is a transaction?
  2. BEGIN and COMMIT
  3. ROLLBACK
  4. SAVEPOINT
  5. ACID
  6. Summary - Transaction

19 ALTER and DROP

  1. ALTER TABLE
  2. Adding a column
  3. Dropping a column
  4. Changing a column type
  5. DROP TABLE
  6. Summary - ALTER and DROP

20 Intermediate final

  1. Multi-JOIN report
  2. Aggregate analysis
  3. Subquery challenge
  4. Transaction scenario