154.CONCAT() 返回两个字符串的连接. SELECTCONCAT(EMP_NO,EMP_NAM)FROMBSEMPMS; 155.YEAR() 返回数值的年部分. SELECTYEAR(''2003/01/02'')FROMBSEMPMS; 156.VARCHAR() 返回字符串,日期型,图形串的可变长度的字符串表示. SELECTVARCHAR(EMP_NAM,50)FROMBSEMPMS; 157.U

46.如何快速清除一个大表? ALTERTABLETABLE_NAMEACTIVENOTLOGGEDINITALLYWITHEMPTYTABLE ALTERTABLETABLE_NAMEACTIVENOTLOGGEDINITALLYWITHEMPTYTABLE 两个commit之间的delete动作是不记日志的 commit altertableabactivatenotloggedintially deleteabwhereid1000 commit （创建的表ab不记录日志：createtableab(id