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Multiple EXISTS

Combine several EXISTS with AND/OR.

Multiple EXISTS

You can combine multiple EXISTS clauses with AND and OR.

SELECT name FROM customers c
WHERE EXISTS (SELECT 1 FROM orders o WHERE o.customer_id = c.id)
  AND EXISTS (SELECT 1 FROM reviews r WHERE r.customer_id = c.id);

This query returns those with both orders and reviews.

name is selected from customers c. WHERE keeps only the rows where EXISTS (SELECT 1 FROM orders o WHERE o.customer_id = c.id) … holds.

Multiple EXISTS — details

Each EXISTS is a separate subquery. AND requires both, OR at least one.

For example, you find customers with both an order and a review using AND, and those with either one using OR.

Practice Multiple EXISTS

Find customers with both orders and reviews using two EXISTS and AND.

Starter code

query.sql
-- two conditions
SELECT name FROM customers c
WHERE

Sample solution

query.sql
SELECT name FROM customers c
WHERE EXISTS (SELECT 1 FROM orders o WHERE o.customer_id = c.id)
  AND EXISTS (SELECT 1 FROM reviews r WHERE r.customer_id = c.id);

Expected output

name
Ayşe

Questions and answers

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

1 Add AND

Question 
WHERE EXISTS (SELECT 1 FROM orders o WHERE o.customer_id = c.id)
  ____ EXISTS (SELECT 1 FROM reviews r WHERE r.customer_id = c.id);
Answer 
WHERE EXISTS (SELECT 1 FROM orders o WHERE o.customer_id = c.id)
  AND EXISTS (SELECT 1 FROM reviews r WHERE r.customer_id = c.id);

Explanation: With two EXISTS conditions joined by AND, the customer must have both an order and a review.

2 Multiple EXISTS: match the terms

Term Meaning
AND both
OR at least one
EXISTS existence
NOT not

3 What does AND with two EXISTS require?

  • Only the first
  • Only one of them
  • None
  • Both of them Correct answer

Explanation: AND requires both EXISTS to be true.

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