sql join expression ambiguous : my ddl script is as follow:

    CREATE TABLE  CPR_ENTITIES
   (	
		 ENTITY_ID NUMBER(20) NOT NULL,

		 SYSTEM_ID NUMBER(4),
		 ENTITY_TYPE_ID NUMBER(8),
		 GLOBAL_UID  VARCHAR2(1000),
		 SYS_OBJ_UID VARCHAR2(1000),
		 ENTITY_NAME VARCHAR2(1000),
		 CAGE_CODE VARCHAR2(2000),
		 REVISION VARCHAR2(2000),
		 ENTITY_CREATION_DATE NUMBER(20),
		 ENTITY_MODIFICATION_DATE NUMBER(20),
		 RELEASE_DATE NUMBER(20),
         .......................,
         ........................
          CONSTRAINT "CPR_ENTITIES_PK" PRIMARY KEY ("ENTITY_ID"),
		 CONSTRAINT "CPR_ENTITIES_FK1" FOREIGN KEY ("SYSTEM_ID") REFERENCES CPR_SOURCE_SYSTEM_METADATA("SYSTEM_ID"),
		 CONSTRAINT "CPR_ENTITIES_FK2" FOREIGN KEY ("ENTITY_TYPE_ID") REFERENCES CPR_ENTITY_METADATA("ENTITY_TYPE_ID"));

       

    CREATE TABLE CPR_ENTITY_ATTRIBUTE 
   (	
		 VAL_ID  NUMBER(20) NOT NULL,

		 ENTITY_ID NUMBER(20),
		 ATT_ID NUMBER(10),
		 STRING_VALUE VARCHAR2(4000),
		 NUM_VALUE NUMBER(10,2),
		 TIMESTAMP_VALUE TIMESTAMP,
		 CREATED_BY VARCHAR2(200),
		 MODIFIED_BY VARCHAR2(200),
		 CREATED_ON NUMBER(20),
		 MODIFIED_ON NUMBER(20),
	         IS_DELETED VARCHAR2(1),	
		 CONSTRAINT "CPR_ENTITY_ATTRIBUTE_PK" PRIMARY KEY ("VAL_ID"),
		 CONSTRAINT "CPR_ENTITY_ATTRIBUTE_FK1" FOREIGN KEY ("ENTITY_ID") REFERENCES CPR_ENTITIES("ENTITY_ID"),
    		 CONSTRAINT "CPR_ENTITY_ATTRIBUTE_FK2" FOREIGN KEY ("ATT_ID") REFERENCES CPR_ENTITY_ATTRIBUTE_METADATA("ATT_ID")
 );

JOIN Expression:

         

     SELECT CPR_ENTITIES.ENTITY_ID,CPR_ENTITY_ATTRIBUTE.STRING_VALUE FROM CPR_ENTITIES LEFT JOIN CPR_ENTITIES ON CPR_ENTITIES.ENTITY_ID=CPR_ENTITY_ATTRIBUTE.ENTITY_ID;

Error given:
ERROR at line 1:
ORA-00904: "CPR_ENTITY_ATTRIBUTE"."ENTITY_ID": invalid identifier