是否可以在 oracle table 中使多个列组合起来唯一？

Question

问题可能不是那么好理解

我创建了两个 tables - 电影 (FILMAS) 和电影院 (ZALES)。他们之间的关系是 M:M，因此 table 会话（SEANSI）是为 link 他们创建的。

是否可以保证同一日期同一时间同一影厅内不能有两场不同的场次？怎么样？

Oracle 18c XE 数据库

CREATE SEQUENCE zlid_seq;

CREATE TABLE ZALES(
    Z_ID INTEGER DEFAULT zlid_seq.NEXTVAL CONSTRAINT ZL_PK PRIMARY KEY,
    ZNOSAUKUMS VARCHAR2(10) NOT NULL UNIQUE,
    IETILPIBA INTEGER NOT NULL,
    ATVERTS BOOLEAN DEFAULT(YES),
    ID_K INTEGER,
    CONSTRAINT SAITE_KT FOREIGN KEY (ID_K) REFERENCES KINOTEATRI(K_ID)
);
CREATE TABLE FILMAS(
    F_ID INTEGER CONSTRAINT FM_PK PRIMARY KEY,
    FNOSAUKUMS VARCHAR2(20) NOT NULL UNIQUE,
    PR_DATUMS DATE NOT NULL,
    ZANRS VARCHAR(20) NOT NULL,
    CONSTRAINT FM_ZN CHECK (ZANRS IN ('ANIMACIJAS','KOMEDIJA','PIEDZIVOJUMU','ŠAUSMU','VESTURISKAIS','DRAMA'))
);
CREATE TABLE SEANSI(
    SDATUMS DATE NOT NULL,
    LAIKS TIME NOT NULL,
    ID_F INTEGER,
    ID_Z INTEGER,
    VALODA VARCHAR(2) DEFAULT 'LATVIESU' NOT NULL,
    CONSTRAINT FM_VAL CHECK (VALODA IN ('LATVIESU', 'KRIEVU', 'ANGLU')),
    CONSTRAINT SAITE_S_FM FOREIGN KEY (ID_F) REFERENCES FILMAS(F_ID),
    CONSTRAINT SAITE_S_ZL FOREIGN KEY (ID_Z) REFERENCES ZALES(Z_ID)
);

Answer 1

是对（日期，时间，ID_z）的唯一约束

CREATE TABLE SEANSI(
    SDATUMS DATE NOT NULL,
    LAIKS TIME NOT NULL,
    ID_F INTEGER,
    ID_Z INTEGER,
    VALODA VARCHAR(2) DEFAULT 'LATVIESU' NOT NULL,
    CONSTRAINT FM_VAL CHECK (VALODA IN ('LATVIESU', 'KRIEVU', 'ANGLU')),
    CONSTRAINT SAITE_S_FM FOREIGN KEY (ID_F) REFERENCES FILMAS(F_ID),
    CONSTRAINT SAITE_S_ZL FOREIGN KEY (ID_Z) REFERENCES ZALES(Z_ID),
    CONSTRAINT UQ_SEANSI UNIQUE (SDATUMS ,LAIKS, ID_z) -- here
);

Answer 2

Is it possible to ensure that at the same date and time there can not be two different sessions in one cinema hall? How?

您需要一个唯一约束（或索引）。您可以使用 table:

声明

CREATE TABLE SEANSI(
    SDATUMS DATE NOT NULL,
    LAIKS TIME NOT NULL,
    ID_F INTEGER,
    ID_Z INTEGER,
    VALODA VARCHAR(2) DEFAULT 'LATVIESU' NOT NULL,
    CONSTRAINT FM_VAL CHECK (VALODA IN ('LATVIESU', 'KRIEVU', 'ANGLU')),
    CONSTRAINT SAITE_S_FM FOREIGN KEY (ID_F) REFERENCES FILMAS(F_ID),
    CONSTRAINT SAITE_S_ZL FOREIGN KEY (ID_Z) REFERENCES ZALES(Z_ID),
    CONSTRAINT UNQ_SEANSI_SDATUMS_LAIK_IDZ UNIQUE (SDATUMS, LAIK, ID_Z)
);

约束保证每个 date/time 和 zales 一行——所以，一部电影。

Answer 3

您可以在这四列上创建唯一约束。此约束将强制组合为您想要的唯一。

ALTER TABLE SEANSI
  add CONSTRAINT SEANSI_unique UNIQUE (SDATUMS , LAIKS , ID_F ,ID_Z );

或者，如果您想在创建 table 时创建约束，则：

CREATE TABLE SEANSI(
    SDATUMS DATE NOT NULL,
    LAIKS TIME NOT NULL,
    ID_F INTEGER,
    ID_Z INTEGER,
    VALODA VARCHAR(2) DEFAULT 'LATVIESU' NOT NULL,
    CONSTRAINT FM_VAL CHECK (VALODA IN ('LATVIESU', 'KRIEVU', 'ANGLU')),
    CONSTRAINT SAITE_S_FM FOREIGN KEY (ID_F) REFERENCES FILMAS(F_ID),
    CONSTRAINT SAITE_S_ZL FOREIGN KEY (ID_Z) REFERENCES ZALES(Z_ID),
    CONSTRAINT SEANSI_unique UNIQUE (SDATUMS , LAIKS , ID_F ,ID_Z )
);

是否可以在 oracle table 中使多个列组合起来唯一？

Is it possible to make more than one columns combinedly unique in a oracle table?

sql

database

oracle

constraints