以下语句错误的是( ) A: alter table emp delete column addcolumn; B: alter table emp modify column addcolumn char(10); C: alter table emp change addcolumn addcolumn int; D: alter table emp add column addcolumn int;

WhichclauseshouldbeincludedinaALTERTABLEstatementtoupdateatabledefinitionwithanew column? A: ADDCOLUMN B: ALTERCOLUMN C: APPENDCOLUMN D: RENAMECOLUMN

更改“成绩表”以添加新列“column_a”CREATETABLE成绩表ADDcolumn_aVARCHAR(20)NULL

更改“成绩表”以添加新列“column_a”_CREATETABLE成绩表ADDcolumn_aVARCHAR(20)NULL