[英]Can't create a table in mySQL
I am trying a table where the primary keys are foreing keys of a table where the primary keys are foreing keys, but it doesn't create the table and I don't know why its not creating.我正在尝试一个表,其中主键是主键是外键的表的外键,但它不创建表,我不知道为什么它不创建。
Table that I want to create:我要创建的表:
CREATE TABLE proj__exames(
floor NUMERIC(2),
room NUMERIC(3),
name VARCHAR(40),
PRIMARY KEY (floor, room, name),
FOREIGN KEY (floor) REFERENCES proj__rooms (floor) ON DELETE CASCADE,
FOREIGN KEY (room) REFERENCES proj__rooms (room) ON DELETE CASCADE,
FOREIGN KEY (name) REFERENCES proj__rooms (name) ON DELETE CASCADE
);
Table where I am getting the foreign key from (this was created without any problems)我从中获取外键的表(创建时没有任何问题)
CREATE TABLE proj__rooms(
floor NUMERIC(2),
room NUMERIC(3),
name VARCHAR(40),
equipment_type VARCHAR(40),
max_exam_number NUMERIC(2) NOT NULL,
-- ========
CONSTRAINT pk_rooms
PRIMARY KEY (name, floor, room),
-- ========
CONSTRAINT fk_salas_nome
FOREIGN KEY (name)
REFERENCES clinic (name) ON DELETE CASCADE,
-- ========
CONSTRAINT ck_rooms_max_exam_number
CHECK (max_exam_number >= 0)
);
The error turned out to be missing indexes on the referenced columns.错误原来是引用列上缺少索引。 Basically you'd have to restructure the
proj__rooms
DDL like this:基本上你必须像这样重组
proj__rooms
DDL:
CREATE TABLE proj__rooms(
floor NUMERIC(2),
room NUMERIC(3),
name VARCHAR(40),
equipment_type VARCHAR(40),
max_exam_number NUMERIC(2) NOT NULL,
-- ========
CONSTRAINT pk_rooms
PRIMARY KEY (name, floor, room),
KEY(floor),
KEY(room),
KEY(name),
-- ========
CONSTRAINT fk_salas_nome
FOREIGN KEY (name)
REFERENCES clinic (name) ON DELETE CASCADE,
-- ========
CONSTRAINT ck_rooms_max_exam_number
CHECK (max_exam_number >= 0)
);
I also suggest you to add the MySQL console error in futher questions, it could make it easier to understand the problem you're facing我还建议您在进一步的问题中添加 MySQL 控制台错误,这样可以更容易理解您面临的问题
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