... statement adds the new tag performance to the first col-umn that is currently null. However, if none of the three columns isnull, then the statement makes no change to the row, and the new tagvalue ... several users’ accounts, but the nature of each association is unique. One is the user who reported the bug, another is a programmer assigned to fix the bug, and another is the quality control engineer ... es.Forexample, he may ask for a count of all open bugs regardless of the year they were created. You can reconstruct the full set of bugs using aUNION of all the split tables and query that as...