正在加载图片...
Duplicate Removal SQL allows duplicates in relations as well as in query results. Use select distinct to force the elimination of duplicates Find the names of all branches in the loan relation and remove duplicates select distinct branch-name force the dbms to remove duplicates from loan The keyword all specifies that duplicates are not removed select all branch-name force the dbms not from loan to remove duplicates COMP3311 Fall 2011 CSE, HKUST Slide 6COMP3311 Fall 2011 CSE, HKUST Slide 6 Duplicate Removal • SQL allows duplicates in relations as well as in query results. Use select distinct to force the elimination of duplicates. Find the names of all branches in the loan relation, and remove duplicates select distinct branch-name from loan • The keyword all specifies that duplicates are not removed. select all branch-name from loan force the DBMS to remove duplicates force the DBMS not to remove duplicates
<<向上翻页向下翻页>>
©2008-现在 cucdc.com 高等教育资讯网 版权所有