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Description

This error indicates that the MySQL client application is attempting to send a new command to the server before the results or status of a previous command have been fully processed or cleared. It typically occurs when the client's expectation of the server's state does not match the actual state, leading to an out-of-sync condition.

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Error Message

Commands out of sync; you can't run this command now

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Known Causes

3 known causes

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Unprocessed Result Sets

A previous SQL query returned a result set, but the client application did not fully fetch or close all rows before attempting another command.

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Improper Result Handling

Mixing or incorrectly using different result-handling functions (e.g., `mysql_store_result()` vs. `mysql_use_result()`) or not clearing previous results.

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Concurrent Operations

Attempting to run a new command while a stored procedure is still executing or has multiple unprocessed result sets.

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Solutions

4 solutions available

1. Consume All Result Sets easy

Ensure all pending result sets from previous queries are fully processed.

1

In your application code, after executing a query that returns a result set (like `SELECT`), iterate through and fetch all rows. If you are using a client library, there's usually a method to clear or consume the results.

# Example in Python with mysql.connector
cursor.execute('SELECT * FROM my_table;')
results = cursor.fetchall()
# Even if you don't need results, fetch them to clear the buffer
# cursor.fetchall() # or similar method depending on library

2

If you've executed a stored procedure or a query that might return multiple result sets, ensure you consume all of them before attempting another query.

# Example in Python for multiple result sets
cursor.callproc('my_stored_procedure', [arg1, arg2])
for result in cursor.stored_results():
    rows = result.fetchall()
    # Process rows if needed

2. Handle Prepared Statements Correctly medium

Ensure prepared statements are executed and results are fetched properly.

1

When using prepared statements, execute the statement first, then fetch the results. Do not attempt to execute another statement before fetching all results from the prepared statement.

# Example in PHP with PDO
$stmt = $pdo->prepare('SELECT * FROM users WHERE id = :id');
$stmt->execute([':id' => $user_id]);
$user = $stmt->fetch();

// Now it's safe to execute another query or prepare a new statement.

2

If you've executed a prepared statement and don't need the results, you still need to clear them from the buffer before executing another command. Most libraries provide a way to do this.

# Example in PHP with PDO (clearing results)
$stmt = $pdo->prepare('SELECT * FROM logs');
$stmt->execute();
while ($row = $stmt->fetch()) {
    // Optionally process or discard row
}
// After the loop, the results are consumed.

3. Restart the Connection or Client easy

A quick way to reset the connection state if other methods fail.

1

Close the current database connection and open a new one. This will reset the client's state and clear any lingering command synchronization issues.

# Example in Python (conceptual)
connection.close()
connection = mysql.connector.connect(...) # Re-establish connection

2

If you are using a GUI tool (like MySQL Workbench, DBeaver, phpMyAdmin), close the current query tab or disconnect and reconnect to the database. If the issue persists, try restarting the tool itself.

4. Review Stored Procedure Logic advanced

Ensure stored procedures are designed to return results sequentially and consistently.

1

If the error occurs when calling a stored procedure, examine the procedure's code. It might be executing multiple statements without properly handling their results, or it might be attempting to execute a new statement before returning from a previous one.

-- Example of a problematic stored procedure snippet
-- CREATE PROCEDURE multi_result_issue ()
-- BEGIN
--   SELECT * FROM table1;
--   -- Missing handling for results of table1 before executing next statement
--   SELECT * FROM table2;
-- END;

-- Corrected approach might involve selecting results in sequence
-- or ensuring the client consumes each result set.

2

Ensure that within a stored procedure, if you execute a `SELECT` statement, you either fetch its results within the procedure (if the procedure is designed to return them) or that the client calling the procedure is prepared to handle multiple result sets.

-- Example of a stored procedure that returns multiple result sets
-- CREATE PROCEDURE get_data ()
-- BEGIN
--   SELECT * FROM products;
--   SELECT * FROM orders;
-- END;

-- The client must then be able to fetch both result sets.

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Related Errors

5 related errors

MySQL Error 2014: Commands Out of Sync