合并union和unionall用法sql结果

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1、合并union和unionall用法-sql语句查询结果--合并重复行select*fromAunionselect*fromB--不合并重复行select*fromAunionallselect*fromB按某个字段排序--合并重复行select*from(select*fromAunionselect*fromB)ASTorderby字段名--不合并重复行select*from(select*fromAunionallselect*fromB)ASTorderby字段名//sqlserver版Select*From(selecttop2id,add

2、date,title,urlfrombArticlewhereClassId='1'orderbyadddatedesc)AUnionAllSelect*From(selecttop2id,adddate,title,urlfrombArticlewhereClassId='2'orderbyadddatedesc)BUnionAllSelect*From(selecttop2id,adddate,title,urlfrombArticlewhereClassId='3'orderbyadddatedesc)CUnionAllSelect*From(s

3、electtop2id,adddate,title,urlfrombArticlewhereClassId='4'orderbyadddatedesc)D//mysql版Select*From(selectid,adddate,title,urlfrombArticlewhereClassId='1'orderbyadddatedesclimit0,2)AUnionAllSelect*From(selectid,adddate,title,urlfrombArticlewhereClassId='2'orderbyadddatedesclimit0,2

4、)BUnionAllSelect*From(selectid,adddate,title,urlfrombArticlewhereClassId='3'orderbyadddatedesclimit0,2)CUnionAllSelect*From(selectid,adddate,title,urlfrombArticlewhereClassId='4'orderbyadddatedesclimit0,2)D在DB2里使用union时一定要注意相对应的字段一定是数据类型一样，输出时可以任意显示的列，但不能输出不同类型或不同表结构。因为这样会出错。