Hash indexes in DBMS Theory - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a hash index on the column 'user_id'.

DBMS Theory

CREATE INDEX idx_user_id ON users USING [1] (user_id);

Drag options to blanks, or click blank then click option'

Abtree

Bgist

Cgin

Dhash

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'btree' which is the default but not a hash index.

Using 'gist' or 'gin' which are for other index types.

The hash keyword specifies that the index uses a hash structure, which is efficient for equality searches.

2fill in blank

medium

Complete the code to query a table using a hash index efficiently.

DBMS Theory

SELECT * FROM orders WHERE order_id [1] 12345;

Drag options to blanks, or click blank then click option'

A>

B=

C<

DLIKE

Attempts:

3 left

💡 Hint

Common Mistakes

Using range operators like '>' or '<' which hash indexes do not support efficiently.

Using 'LIKE' which is for pattern matching.

Hash indexes are optimized for equality comparisons using the = operator.

3fill in blank

hard

Fix the error in the statement to create a hash index in PostgreSQL.

DBMS Theory

CREATE INDEX idx_email ON customers USING [1] (email);

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Ahash

Bbtree

Ctext

Dindex

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'text' which is a data type, not an index type.

Using 'index' which is not a valid index method.

PostgreSQL supports hash indexes using the hash keyword. Using 'btree' creates a different index type, and 'text' or 'index' are invalid here.

4fill in blank

hard

Fill both blanks to create a hash index and ensure it is used for equality searches.

DBMS Theory

CREATE INDEX idx_product_id ON products USING [1] (product_id);
SELECT * FROM products WHERE product_id [2] 100;

Drag options to blanks, or click blank then click option'

Ahash

B=

C>

Dbtree

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'btree' for the index type when the question asks for a hash index.

Using '>' instead of '=' in the WHERE clause.

The first blank must be 'hash' to create a hash index. The second blank must be '=' because hash indexes support equality comparisons.

5fill in blank

hard

Fill all three blanks to create a hash index, query with equality, and explain the limitation of hash indexes.

DBMS Theory

CREATE INDEX idx_customer_id ON customers USING [1] (customer_id);
SELECT * FROM customers WHERE customer_id [2] 500;
-- Note: Hash indexes do not support [3] searches efficiently.

Drag options to blanks, or click blank then click option'

Ahash

B=

Crange

Dbtree

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'btree' instead of 'hash' for the index type.

Using operators other than '=' for querying hash indexes.

Not recognizing that range queries are inefficient with hash indexes.

Hash indexes are created with 'hash' and used with '=' for equality searches. They do not support 'range' searches efficiently, which is a key limitation.