How to exclude duplicate lines from $wpdb->prepare?

Question

SQL

There is a bookmark plugin with categories and its table.
From there you need to take the number of posts that the user has bookmarked.
For this I use the following query:

SELECT count(*) as totalobject FROM $cbxwpbookmrak_table WHERE user_id = %d

But if you add one post to 3 different categories, then instead of the number 1, 3 will be displayed, because. in the table, the row is essentially duplicated, only the category id differs

Is it possible to refine the query so that a post that was added to several categories is counted as 1, and not a number equal to the number of categories to which it is added?

Answer 1

SELECT COUNT(DISTINCT( object_id)) as totalobject FROM $cbxwpbookmrak_table WHERE user_id = %d