How many images have at least one pair of object samples with the relation "parked on"?
How many images have at least one pair of object samples with the relation "parked on" refers to count(IMG_ID) where OBJ1_SAMPLE_ID ! = OBJ2_SAMPLE_ID and PRED_CLASS = 'parked on'
SELECT SUM(CASE WHEN T1.PRED_CLASS = 'parked on' THEN 1 ELSE 0 END) FROM PRED_CLASSES AS T1 INNER JOIN IMG_REL AS T2 ON T1.PRED_CLASS_ID = T2.PRED_CLASS_ID WHERE T2.OBJ1_SAMPLE_ID != T2.OBJ2_SAMPLE_ID
CREATE TABLE ATT_CLASSES
(
    ATT_CLASS_ID INTEGER default 0 not null
        primary key,
    ATT_CLASS    TEXT      not null
);
CREATE TABLE OBJ_CLASSES
(
    OBJ_CLASS_ID INTEGER default 0 not null
        primary key,
    OBJ_CLASS    TEXT      not null
);
CREATE TABLE IMG_OBJ
(
    IMG_ID        INTEGER default 0 not null,
    OBJ_SAMPLE_ID INTEGER    default 0 not null,
    OBJ_CLASS_ID  INTEGER              null,
    X             INTEGER              null,
    Y             INTEGER             null,
    W             INTEGER              null,
    H             INTEGER              null,
    primary key (IMG_ID, OBJ_SAMPLE_ID),
    foreign key (OBJ_CLASS_ID) references OBJ_CLASSES (OBJ_CLASS_ID)
);
CREATE TABLE IMG_OBJ_ATT
(
    IMG_ID        INTEGER default 0 not null,
    ATT_CLASS_ID  INTEGER    default 0 not null,
    OBJ_SAMPLE_ID INTEGER    default 0 not null,
    primary key (IMG_ID, ATT_CLASS_ID, OBJ_SAMPLE_ID),
    foreign key (ATT_CLASS_ID) references ATT_CLASSES (ATT_CLASS_ID),
    foreign key (IMG_ID, OBJ_SAMPLE_ID) references IMG_OBJ (IMG_ID, OBJ_SAMPLE_ID)
);
CREATE TABLE PRED_CLASSES
(
    PRED_CLASS_ID INTEGER default 0 not null
        primary key,
    PRED_CLASS    TEXT     not null
);
CREATE TABLE IMG_REL
(
    IMG_ID         INTEGER default 0 not null,
    PRED_CLASS_ID  INTEGER    default 0 not null,
    OBJ1_SAMPLE_ID INTEGER    default 0 not null,
    OBJ2_SAMPLE_ID INTEGER   default 0 not null,
    primary key (IMG_ID, PRED_CLASS_ID, OBJ1_SAMPLE_ID, OBJ2_SAMPLE_ID),
    foreign key (PRED_CLASS_ID) references PRED_CLASSES (PRED_CLASS_ID),
    foreign key (IMG_ID, OBJ1_SAMPLE_ID) references IMG_OBJ (IMG_ID, OBJ_SAMPLE_ID),
    foreign key (IMG_ID, OBJ2_SAMPLE_ID) references IMG_OBJ (IMG_ID, OBJ_SAMPLE_ID)
);
