No. You cannot specify which exact field you need to distinct with. It only works with the whole row. As of your problem - just make your ... ... <看更多>

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ad 1) Old mysql databases and when you disable ONLY_FULL_GROUP_BY , you can make this query and if the post_content are all equal you would ... ... <看更多>

In mysql 5.7 it is required to have the order by fields to be present in the select statement when using DISTINCT. I have situated where the ... ... <看更多>