Hi,
I have a problem with a field. I created a join table on lookerstudio, but if I read a field of a table this is incorrect. The same field without join table is correct.
When a field value changes after you join tables in Looker Studio, it usually means the join key or join type is creating duplicate or mismatched rows. Looker Studio performs a record-level join in-memory, so if your join key isn’t unique in both tables, numeric or aggregated fields can multiply or distort. You can confirm this by checking the join configuration under Resource > Manage blends and reviewing the join relationship and aggregation behavior for that field.
To fix it, ensure the field you’re joining on is unique in at least one of the tables or pre-aggregate the data in MySQL before connecting. If you need to maintain a one-to-many relationship, try using calculated fields or a grouped data source in Looker Studio that summarizes the MySQL data first, then blend that result with the Google Ads metrics. This keeps your metrics consistent and prevents inflated totals after the join.
—Taz