sql自联接表删除重复的行

使用您的标识符：

SELECt a.userId , a.LanguageId, b.LanguageId  FROM knownlanguages a inner join knownlanguages b      on a.userID=b.userID and a.LanguageId < b.LanguageId

测试：FOT表：

create table t ( u int, l int);insert into t values (    1,    2),(    1,    7),(    1,    8),(    2,    10),(    2,    3);

查询是：

select t1.u, t1.l as l1, t2.l as l2from t t1 inner join t t2   on t1.u = t2.u and t1.l < t2.l

（结果）