👀 Views: 78 💬 Answers: 1 📅 Created: 2025-06-05

mysql insert-ignore unique-keys sql

I'm working on a project and hit a roadblock... I'm a bit lost with I'm trying to configure I've searched everywhere and can't find a clear answer. I'm working on a project and hit a roadblock. I'm facing a perplexing issue with MySQL where duplicate entries are somehow getting inserted into my table despite using `INSERT IGNORE`. My table has a composite unique key constraint on the columns `user_id` and `event_timestamp`. The issue arises specifically when the `event_timestamp` values are very close to each other. Here's the relevant part of my table definition: ```sql CREATE TABLE user_events ( user_id INT, event_timestamp DATETIME, event_type VARCHAR(50), PRIMARY KEY (user_id, event_timestamp) ); ``` When I run the following insert statement: ```sql INSERT IGNORE INTO user_events (user_id, event_timestamp, event_type) VALUES (1, '2023-10-01 12:00:00', 'login'); INSERT IGNORE INTO user_events (user_id, event_timestamp, event_type) VALUES (1, '2023-10-01 12:00:00.0001', 'logout'); ``` I expect the second insert to be ignored because the timestamp is supposed to be unique. However, both records are inserted into the table. I have confirmed that the precision of the `DATETIME` data type is set to 6 in my MySQL setup, which should allow for microsecond precision. I also tried using `INSERT ... ON DUPLICATE KEY UPDATE` instead of `INSERT IGNORE`, but that doesn't prevent duplicates either. To troubleshoot, I executed: ```sql SHOW CREATE TABLE user_events; SELECT * FROM user_events; ``` And the results show both entries exist. I also ensured that there are no triggers or foreign key constraints that could be affecting the behavior. Is there a known issue with composite unique keys and precision when using `INSERT IGNORE` in MySQL 8.0.28, or am I missing something fundamental in my approach? Any insights or solutions would be greatly appreciated! This is part of a larger web app I'm building. Has anyone else encountered this? I'm working on a application that needs to handle this. Am I missing something obvious? What would be the recommended way to handle this? I'd be grateful for any help. I'm working in a Ubuntu 20.04 environment. I'd be grateful for any help.