When working with MySQL, you might encounter Error 1134 – SQLSTATE: HY000 (ER_UPDATE_INFO), which is not so much an error as it is a message providing information after executing an
UPDATE statement. The message
Rows matched: %ld Changed: %ld Warnings: %ld gives you a breakdown of the number of rows that matched the
WHERE clause criteria, how many were actually changed, and the number of warnings that occurred during the operation. This message can help you understand the behavior of your
UPDATE statements and diagnose potential issues.
Understanding the Message
This informational message is MySQL’s way of telling you the outcome of an
UPDATE operation. It is important because it can indicate cases where rows may match the criteria but are not changed because the new value is the same as the old value, or due to the use of
SAFE UPDATES mode, which prevents updates without a key in the
WHERE clause or a limit in the
Diagnosing the Issue
To diagnose the issue, you need to examine the
UPDATE statement and the table’s data. Check for the following:
- Are the values being updated actually different from the existing values?
- Is the
WHEREclause written correctly to match the intended rows?
- Are there any triggers or constraints on the table that might prevent the update?
SAFE UPDATESmode enabled which might be preventing the update?
Example Scenarios and Fixes
Scenario 1: Updating to the Same Value
UPDATE statement is setting a column to its current value.
UPDATE users SET name = 'John Doe' WHERE name = 'John Doe';
-- Rows matched: 1 Changed: 0 Warnings: 0
Fix: Ensure the new value is different from the old value.
Scenario 2: Incorrect
WHERE clause does not match any rows.
UPDATE users SET name = 'Jane Doe' WHERE id = 999;
-- Rows matched: 0 Changed: 0 Warnings: 0
Fix: Correct the
WHERE clause to match the intended rows.
Scenario 3: Triggers or Constraints
Problem: A trigger or constraint is preventing the update.
-- Assuming there is a trigger that prevents updating username to 'admin'
UPDATE users SET username = 'admin' WHERE id = 1;
Fix: Modify or remove the trigger or constraint that is interfering with the update.
Scenario 4: SAFE UPDATES Mode
SAFE UPDATES mode is enabled, preventing updates without a key in the
SET SQL_SAFE_UPDATES = 1;
UPDATE users SET name = 'Jane Doe';
-- Error: You are using safe update mode...
Fix: Use a key in the
WHERE clause or disable
SAFE UPDATES mode.
UPDATE users SET name = 'Jane Doe' WHERE id = 1; -- Using a key
SET SQL_SAFE_UPDATES = 0; -- Disabling SAFE UPDATES
MySQL Error 1134 provides valuable information about the result of an
UPDATE operation. Understanding this message can help you ensure that your
UPDATE statements are functioning as intended. By examining the
UPDATE statement, the table’s data, and any relevant database settings, you can diagnose and address issues that may be preventing your updates from taking effect as expected.