This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
When you create a database, you can specify that values in certain columns must meet certain conditions. If those conditions are not met, then you get a constraint violation error. Often this means that two records have the same key value (unique key values are often implied constraints). Check the data you are inserted to see of two records have the same key.