Transaction isolation levels in SQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

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

SQL

SET TRANSACTION ISOLATION LEVEL [1];

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AREAD UNCOMMITTED

BSERIALIZABLE

CREPEATABLE READ

DREAD COMMITTED

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing READ UNCOMMITTED causes dirty reads.

Choosing SERIALIZABLE is stricter than needed here.

The READ COMMITTED level allows a transaction to see only committed data, preventing dirty reads.

2fill in blank

medium

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

SQL

START TRANSACTION ISOLATION LEVEL [1];

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ASERIALIZABLE

BREAD COMMITTED

CREPEATABLE READ

DREAD UNCOMMITTED

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing REPEATABLE READ does not prevent phantom reads.

Choosing READ COMMITTED allows some concurrency anomalies.

SERIALIZABLE is the strictest isolation level, preventing all concurrency anomalies.

3fill in blank

hard

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

SQL

SET TRANSACTION ISOLATION [1] REPEATABLE READ;

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ATO

BMODE

CLEVEL

DWITH

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'MODE' instead of 'LEVEL' causes syntax errors.

Omitting the keyword after ISOLATION is invalid.

The correct syntax is SET TRANSACTION ISOLATION LEVEL followed by the level name.

4fill in blank

hard

Fill the three blanks to complete the command that sets the isolation level to READ UNCOMMITTED for the current session.

SQL

SET SESSION TRANSACTION ISOLATION [1] [2] [3];

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ALEVEL

BREAD

CUNCOMMITTED

DMODE

Attempts:

3 left

💡 Hint

Common Mistakes

Using MODE instead of LEVEL causes errors.

Missing the isolation level name after LEVEL.

The correct syntax is SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;. This is the least strict isolation level, allowing dirty reads.

5fill in blank

hard

Fill all three blanks to write a query that shows the current transaction isolation level.

SQL

SELECT @@transaction_isolation AS [1], @@[2] AS [3];

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Acurrent_level

Btx_isolation

Csession_level

Disolation_level

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect variable names causes errors.

Not aliasing columns makes output less clear.

This query selects the current transaction isolation level using system variables. '@@transaction_isolation' is standard, '@@tx_isolation' is a synonym in some systems, and aliasing helps readability.