Criação de tabelas

--GENERATOR INTERNO DISPONIVEL NO FIREBIRD 3.0 EM DIANTE
CREATE TABLE VENDAS
(
    ID INTEGER GENERATED BY DEFAULT AS IDENTITY,
    DATA DATE,
    CONSTRAINT PK_VENDAS_ID PRIMARY KEY (ID)
);

CREATE TABLE VENDAS_ITENS
(
    ID INTEGER GENERATED BY DEFAULT AS IDENTITY,
    ID_VENDA INTEGER,
    DESCR VARCHAR(60) CHARACTER SET WIN1252 COLLATE WIN_PTBR,
    VALOR_UN NUMERIC(15,4),
    QTD NUMERIC(15,4),
    DESCONTO NUMERIC(15,4),
    TOTAL NUMERIC(15,4) COMPUTED BY ((VALOR_UN * QTD) - DESCONTO),
    CONSTRAINT PK_VENDAS_ITENS_ID PRIMARY KEY (ID),
    CONSTRAINT FK_VENDAS_ID FOREIGN KEY (ID_VENDA) REFERENCES VENDAS (ID) ON DELETE CASCADE
);

--OBS: RESETAR GENERATOR QUANDO NECESSARIO
ALTER TABLE VENDAS ALTER COLUMN ID RESTART WITH 0;