Transaction isolation levels in PostgreSQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the transaction isolation level to READ COMMITTED in PostgreSQL.

PostgreSQL

SET TRANSACTION ISOLATION LEVEL [1];

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AREAD UNCOMMITTED

BSERIALIZABLE

CREPEATABLE READ

DREAD COMMITTED

Attempts:

3 left

💡 Hint

Common Mistakes

Using READ UNCOMMITTED which is not supported in PostgreSQL.

Confusing REPEATABLE READ with READ COMMITTED.

The READ COMMITTED level is the default in PostgreSQL and ensures that any data read is committed at the moment it is read.

2fill in blank

medium

Complete the code to start a transaction with SERIALIZABLE isolation level in PostgreSQL.

PostgreSQL

BEGIN TRANSACTION ISOLATION LEVEL [1];

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AREPEATABLE READ

BREAD COMMITTED

CSERIALIZABLE

DREAD UNCOMMITTED

Attempts:

3 left

💡 Hint

Common Mistakes

Using BEGIN without specifying the isolation level.

Choosing REPEATABLE READ instead of SERIALIZABLE.

The SERIALIZABLE isolation level provides the strictest transaction isolation, preventing phenomena like phantom reads.

3fill in blank

hard

Fix the error in the code to set the transaction isolation level to REPEATABLE READ.

PostgreSQL

SET TRANSACTION ISOLATION [1] REPEATABLE READ;

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AAS

BLEVEL

CTO

DWITH

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the keyword LEVEL causes syntax errors.

Using TO or AS instead of LEVEL.

The correct syntax is SET TRANSACTION ISOLATION LEVEL REPEATABLE READ; where LEVEL is required.

4fill in blank

hard

Fill both blanks to complete the command that sets the isolation level to READ UNCOMMITTED (even though PostgreSQL treats it as READ COMMITTED).

PostgreSQL

SET TRANSACTION [1] [2] READ UNCOMMITTED;

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AISOLATION

BLEVEL

CTO

DAS

Attempts:

3 left

💡 Hint

Common Mistakes

Using TO or AS instead of ISOLATION LEVEL.

Swapping the order of the keywords.

The correct syntax is SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED; even though PostgreSQL treats it as READ COMMITTED internally.

5fill in blank

hard

Fill all three blanks to complete the command that starts a transaction with REPEATABLE READ isolation level.

PostgreSQL

BEGIN [1] ISOLATION [2] [3];

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ATRANSACTION

BLEVEL

CREPEATABLE READ

DSESSION

Attempts:

3 left

💡 Hint

Common Mistakes

Using SESSION instead of TRANSACTION after BEGIN.

Omitting LEVEL keyword.

Using wrong isolation level name.

The correct command is BEGIN TRANSACTION ISOLATION LEVEL REPEATABLE READ; to start a transaction with that isolation level.