出现原因，是因为在更新的的表和读取的表是同一个表。
CREATE or replace TRIGGER T_userupdateT BEFORE update ON T_user REFERENCING OLD AS old NEW AS N_ROW FOR EACH ROW
DECLARE U_xtfidemp1 varchar(36);
u_xtempcode1 varchar(20);
u_xtempcodeCount int:=0;
U_xtfidempCount int:=0;
u_id1 int:=0;
BEGIN
U_xtfidemp1:=:N_ROW.U_xtfidemp;
u_xtempcode1:=:N_ROW.u_xtempcode;
u_id1:=:N_ROW.u_id;
select count(u_xtempcode) into u_xtempcodeCount from eas.T_user where u_xtempcode is not null and u_xtempcode=u_xtempcode1 and u_id<>u_id1;
select count(U_xtfidemp) into U_xtfidempCount from eas.T_user where U_xtfidemp is not null and U_xtfidemp=U_xtfidemp1 and u_id<>u_id1;
IF u_xtempcodeCount>0 or U_xtfidempCount>0 THEN
RAISE_APPLICATION_ERROR(-20001, 'eas.T_user u_xtempcode,U_xtfidemp,U_GZCode更新数据时有错误,有重复');
END IF;
end;
出现错误时，是因为触发器在T_userupdateT在T_user上，触发器内部有读取了T_user所以有错误。
修改如下
CREATE or replace TRIGGER T_userupdateT BEFORE update ON T_user REFERENCING OLD AS old NEW AS N_ROW FOR EACH ROW
DECLARE U_xtfidemp1 varchar(36);
u_xtempcode1 varchar(20);
u_xtempcodeCount int:=0;
U_xtfidempCount int:=0;
u_id1 int:=0;
PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
U_xtfidemp1:=:N_ROW.U_xtfidemp;
u_xtempcode1:=:N_ROW.u_xtempcode;
u_id1:=:N_ROW.u_id;
select count(u_xtempcode) into u_xtempcodeCount from eas.T_user where u_xtempcode is not null and u_xtempcode=u_xtempcode1 and u_id<>u_id1;
select count(U_xtfidemp) into U_xtfidempCount from eas.T_user where U_xtfidemp is not null and U_xtfidemp=U_xtfidemp1 and u_id<>u_id1;
IF u_xtempcodeCount>0 or U_xtfidempCount>0 THEN
RAISE_APPLICATION_ERROR(-20001, 'eas.T_user u_xtempcode,U_xtfidemp,U_GZCode更新数据时有错误,有重复');
END IF;
COMMIT;
end;
多了PRAGMA AUTONOMOUS_TRANSACTION;COMMIT;两句
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