CREATE TABLE A (
    ID INTEGER NOT NULL,
    VAL VARCHAR(32) CHARACTER SET UTF8);


CREATE TABLE B1 (
    ID INTEGER NOT NULL,
    ID_A INTEGER NOT NULL,
    NUM INTEGER,
    FIX DATE);


CREATE TABLE B2 (
    ID INTEGER NOT NULL,
    ID_A INTEGER NOT NULL,
    NUM INTEGER,
    FIX DATE);


CREATE TABLE C (
    ID INTEGER NOT NULL,
    ID_A INTEGER NOT NULL,
    FLAG SMALLINT);

ALTER TABLE A ADD CONSTRAINT PK_A PRIMARY KEY (ID);
ALTER TABLE B1 ADD CONSTRAINT PK_B1 PRIMARY KEY (ID);
ALTER TABLE B2 ADD CONSTRAINT PK_B2 PRIMARY KEY (ID);
ALTER TABLE C ADD CONSTRAINT PK_C PRIMARY KEY (ID);

ALTER TABLE B1 ADD CONSTRAINT FK_B1_A FOREIGN KEY (ID_A) REFERENCES A (ID);
ALTER TABLE B2 ADD CONSTRAINT FK_B2_A FOREIGN KEY (ID_A) REFERENCES A (ID);
ALTER TABLE C ADD CONSTRAINT FK_C_A FOREIGN KEY (ID_A) REFERENCES A (ID);

CREATE INDEX IDX_B1_FIX ON B1 (FIX);
CREATE INDEX IDX_B2_FIX ON B2 (FIX);
CREATE INDEX IDX_C_FLAG ON C (FLAG);

SET TERM ^ ;

create or alter function DFST (
    RDAY smallint not null)
returns date not null
as
declare variable RDIFF smallint;
begin
  RDIFF = RDAY - EXTRACT(DAY FROM CURRENT_DATE);
  return IIF(RDIFF < 0,  DATEADD(DAY, RDIFF, CURRENT_DATE), DATEADD(MONTH, -1, DATEADD(DAY, RDIFF, CURRENT_DATE)));
end
^

create or alter function DLST (
    RDAY smallint not null)
returns date not null
as
declare variable RDIFF smallint;
begin
  RDIFF = RDAY - EXTRACT(DAY FROM CURRENT_DATE);
  return IIF(RDIFF < 0,  DATEADD(MONTH, 1, DATEADD(DAY, RDIFF, CURRENT_DATE)), DATEADD(DAY, RDIFF, CURRENT_DATE)) - 1;
end
^

SET TERM ; ^