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  • information_schema.referential_constraints 学习

    information_schema.referential_constraints 表用于查看外键约束

    1、information_schema.referential_constraints表的常用列:

      1、constraint_schema                :约束(外键)所在的库名

      2、constraint_name                  :约束名(外键名)

      3、unique_constraint_schema            :被引用约束所在库名

      4、unique_constraint_name              :被引用约束名

    2、例子:

      1、定义一对有外键约束的表:

    create table teacher(
    id int not null auto_increment,
    name varchar(4),
    constraint pk__teacher primary key(id),
    constraint ix__teacher__name unique index (name))
    engine=innodb default char set utf8;
    
    
    
    create table student(
    id int not null auto_increment,
    name varchar(4),
    teacher_id int not null,
    teacher_name varchar(4),
    constraint pk__student primary key(id),
    constraint fk__student__id foreign key (teacher_id ) references teacher(id),
    constraint fk__student__teacher_name foreign key (teacher_name) references teacher(name) on delete no action on update cascade)
    engine=innodb default char set utf8;

      2、查看外键约束

    select * from information_schema.referential_constraints G
    *************************** 1. row ***************************
           CONSTRAINT_CATALOG: def
            CONSTRAINT_SCHEMA: tempdb
              CONSTRAINT_NAME: fk__student__id
    UNIQUE_CONSTRAINT_CATALOG: def
     UNIQUE_CONSTRAINT_SCHEMA: tempdb
       UNIQUE_CONSTRAINT_NAME: PRIMARY
                 MATCH_OPTION: NONE
                  UPDATE_RULE: RESTRICT
                  DELETE_RULE: RESTRICT
                   TABLE_NAME: student
        REFERENCED_TABLE_NAME: teacher
    *************************** 2. row ***************************
           CONSTRAINT_CATALOG: def
            CONSTRAINT_SCHEMA: tempdb
              CONSTRAINT_NAME: fk__student__teacher_name
    UNIQUE_CONSTRAINT_CATALOG: def
     UNIQUE_CONSTRAINT_SCHEMA: tempdb
       UNIQUE_CONSTRAINT_NAME: ix__teacher__name
                 MATCH_OPTION: NONE
                  UPDATE_RULE: CASCADE
                  DELETE_RULE: NO ACTION
                   TABLE_NAME: student
        REFERENCED_TABLE_NAME: teacher
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  • 原文地址:https://www.cnblogs.com/JiangLe/p/5837195.html
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