Kai Zander ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=557058%... ) *commented* on HHH-15517 ( https://hibernate.atlassian.net/browse/HHH-15517?atlOrigin=eyJpIjoiYWJlMj... ) Re: "insert from select" With hibernate.default_schema Configured Doesn't Work With Hibernate 6 ( https://hibernate.atlassian.net/browse/HHH-15517?atlOrigin=eyJpIjoiYWJlMj... ) I experimented a bit more and found the following: If I rewrite the HQL to this (don’t select id , use distinct instead of group by ): insert into TabData (col1, col2, col3) select distinct col1, col2, col3 from TabDataStaging Hibernate 6 does the following: insert into HTE_tab_data(col1, col2, col3, rn_) ( select distinct p2_0.col1, p2_0.col2, p2_0.col3, row_number () over () -- adding this column effectively disables the ` distinct ` from tab_data_staging p2_0); Followed by the updates on the HTE table you were suspecting earlier: update HTE_tab_data set id=? where rn_=? update HTE_tab_data set id=? where rn_=? ... Followed by insert into tab_data(col1,col2,col3,id) select p1_0.col1,p1_0.col2,p1_0.col3,p1_0.id from HTE_tab_data p1_0 The final insert into tab_data can then fail due to unique constraint violation (I have a composite unique constraint on col1, col2, col3 ), because even though I’m using distinct , the row_number() clause added by Hibernate effectively disabled it… ( https://hibernate.atlassian.net/browse/HHH-15517#add-comment?atlOrigin=ey... ) Add Comment ( https://hibernate.atlassian.net/browse/HHH-15517#add-comment?atlOrigin=ey... ) Get Jira notifications on your phone! Download the Jira Cloud app for Android ( https://play.google.com/store/apps/details?id=com.atlassian.android.jira.... ) or iOS ( https://itunes.apple.com/app/apple-store/id1006972087?pt=696495&ct=Em... ) This message was sent by Atlassian Jira (v1001.0.0-SNAPSHOT#100207- sha1:7afd384 )