Why is my MySQL UPDATE query returning \'0 Rows Affected\'?

MySQL UPDATE Query Returns "0 Rows Affected"

The MySQL UPDATE statement is used to modify the data in an existing table. One common issue encountered is receiving the message "0 rows affected" despite successful query execution.

In this particular case, the UPDATE query aims to update the Called column in the phonecalls table to "Yes" for a specific PhoneNumber. However, the query is returning "0 rows affected."

Understanding the Issue

The message "0 rows affected" indicates that no rows were changed as a result of the executed query. This can happen for several reasons:

• Incorrect Syntax: Ensure that the query syntax is correct.
• Non-existent PhoneNumber: Verify that the specified PhoneNumber actually exists in the database.
• Already Updated: If the Called column is already set to "Yes" for the specified PhoneNumber, the UPDATE query will not make any changes.

Troubleshooting

To resolve this issue, consider the following steps:

1. Check the PhoneNumber: Confirm that the PhoneNumber used in the query matches the correct row in the table.
2. Check the Current Called Value: Use a SELECT query to check the current value of the Called column for the specified PhoneNumber. If it is already set to "Yes," the UPDATE query will not make any changes.
3. Use a WHERE Condition: Specify a specific PhoneNumber in the WHERE clause to ensure that only the desired row is updated. For example:

UPDATE phonecalls SET Called = "Yes" WHERE PhoneNumber = "999 29-4655" AND Called <> "Yes";

By adding the condition Called <> "Yes," the query will only execute if the current value of the Called column is not "Yes."

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