Yes, I have had to troubleshoot issues with join logic in a project. One issue I encountered was when I was trying to join two tables based on a common column, but the values in the common column were not matching between the two tables. This resulted in a lot of null values in the joined table. To resolve this issue, I first checked the data types of the common column in both tables to make sure they were the same. I also checked for any spelling or formatting differences in the values in the common column. If I still couldn't find the issue, I used a process of elimination to narrow down which rows in the tables were causing the issue by performing a series of inner and outer joins. Ultimately, I found that there were some special characters in the common column in one of the tables that were not present in the other table. I cleaned up the data by removing these special characters and reran the join, which resulted in a successful join without any null values. Expect to come across this, one of the most popular SQL JOINs interview questions.