CREATE TABLE "MAINTENANCE"."MAINTENANCE_REQUESTS" 
   (    "DATE_SUBMITTED" DATE CONSTRAINT "CK_DATE_SUBMITTED_NN" NOT NULL ENABLE, 
    "FISCAL_YEAR" VARCHAR2(4 BYTE) DEFAULT '2016' CONSTRAINT "CK_FISCAL_YEAR_NN" NOT NULL ENABLE, 
    "WORK_ORDER" NUMBER(22,0) CONSTRAINT "CK_WORK_ORDER_NN" NOT NULL ENABLE, 
    "SUBMITTED_BY" VARCHAR2(40 BYTE), 
    "PHONE" VARCHAR2(14 BYTE), 
    "ASSIGNED_DATE" DATE, 
    "ASSIGNED_TO" VARCHAR2(50 BYTE), 
    "BUILDING_NUMBER" VARCHAR2(30 BYTE), 
    "ROOM_NUMBER" VARCHAR2(30 BYTE), 
    "PRIORITY_LEVEL" VARCHAR2(60 BYTE), 
    "URGENCY_LEVEL" VARCHAR2(80 BYTE), 
    "MAINTENANCE_ISSUE" VARCHAR2(120 BYTE) CONSTRAINT "CK_MAIN_ISSUE_NN" NOT NULL ENABLE, 
    "WORK_REQUIRED" VARCHAR2(2000 BYTE), 
    "START_DATE" DATE, 
    "END_DATE" DATE, 
    "REOCCUR" NUMBER, 
    "ID" NUMBER CONSTRAINT "CK_ID_MAIN_REQ_NN" NOT NULL ENABLE, 

SQL> create table tbl
  2  as select level lvl from dual connect by level <= 10;

Table created.

SQL> create or replace
  2  trigger tbl_bir
  3  before insert
  4  on tbl
  5  for each row
  6  begin
  7      delete tbl where mod(lvl,2) = mod(:new.lvl,2);
  8  end;
  9  /

Trigger created.

SQL> insert
  2    into tbl
  3    select 11 from dual
  4  /
  into tbl
       *
ERROR at line 2:
ORA-04091: table SCOTT.TBL is mutating, trigger/function may not see it
ORA-06512: at "SCOTT.TBL_BIR", line 2
ORA-04088: error during execution of trigger 'SCOTT.TBL_BIR'


SQL> insert
  2    into tbl
  3    values(11)
  4  /

1 row created.

SQL> select * from tbl
  2  /

       LVL
----------
         2
         4
         6
         8
        10
        11

6 rows selected.

SQL>