如何查找具有引用特定table.column的外键并具有这些外键值的所有表？

Question

我有一个表,其主键在其他几个表中作为外键引用.例如:

  CREATE TABLE `X` (
    `X_id` int NOT NULL auto_increment,
    `name` varchar(255) NOT NULL,
    PRIMARY KEY  (`X_id`)
  )
  CREATE TABLE `Y` (
    `Y_id` int(11) NOT NULL auto_increment,
    `name` varchar(255) NOT NULL,
    `X_id` int DEFAULT NULL,
    PRIMARY KEY  (`Y_id`),
    CONSTRAINT `Y_X` FOREIGN KEY (`X_id`) REFERENCES `X` (`X_id`)
  )
  CREATE TABLE `Z` (
    `Z_id` int(11) NOT NULL auto_increment,
    `name` varchar(255) NOT NULL,
    `X_id` int DEFAULT NULL,
    PRIMARY KEY  (`Z_id`),
    CONSTRAINT `Z_X` FOREIGN KEY (`X_id`) REFERENCES `X` (`X_id`)
  )

现在,我不知道数据库中有多少表包含X中的外键,如表Y和Z.是否有可用于返回的SQL查询:

1. 包含外键到X的表的列表
2. 和哪些表实际上在外键中有值

Answer 1

干得好:

USE information_schema;
SELECT *
FROM
  KEY_COLUMN_USAGE
WHERE
  REFERENCED_TABLE_NAME = 'X'
  AND REFERENCED_COLUMN_NAME = 'X_id';

如果您有多个具有相似表/列名称的数据库,您可能还希望将查询限制为特定数据库:

SELECT *
FROM
  KEY_COLUMN_USAGE
WHERE
  REFERENCED_TABLE_NAME = 'X'
  AND REFERENCED_COLUMN_NAME = 'X_id'
  AND TABLE_SCHEMA = 'your_database_name';

Answer 2

MySQL 5.5参考手册:"InnoDB和FOREIGN KEY约束"

SELECT
  ke.REFERENCED_TABLE_SCHEMA parentSchema,
  ke.referenced_table_name parentTable,
  ke.REFERENCED_COLUMN_NAME parentColumnName,
  ke.TABLE_SCHEMA ChildSchema,
  ke.table_name childTable,
  ke.COLUMN_NAME ChildColumnName
FROM
  information_schema.KEY_COLUMN_USAGE ke
WHERE
  ke.referenced_table_name IS NOT NULL
  AND ke.REFERENCED_COLUMN_NAME = 'ci_id' ## Find Foreign Keys linked to this Primary Key
ORDER BY
  ke.referenced_table_name;

Answer 3

此解决方案不仅会显示所有关系,还会显示约束名称,这在某些情况下是必需的(例如,丢弃约束):

SELECT
    CONCAT(table_name, '.', column_name) AS 'foreign key',
    CONCAT(referenced_table_name, '.', referenced_column_name) AS 'references',
    constraint_name AS 'constraint name'
FROM
    information_schema.key_column_usage
WHERE
    referenced_table_name IS NOT NULL;

如果要检查特定数据库中的表,请添加以下内容:

AND table_schema = 'database_name';

Answer 4

您可以在明智命名的information_schema表中找到所有与架构相关的信息.

您可能要检查表REFERENTIAL_CONSTRAINTS和KEY_COLUMN_USAGE.前者告诉你哪些表被其他人引用; 后者会告诉你他们的领域是如何相关的.

Answer 5

列出数据库中的所有外键，包括描述

    SELECT  
    i1.CONSTRAINT_NAME, i1.TABLE_NAME,i1.COLUMN_NAME,
    i1.REFERENCED_TABLE_SCHEMA,i1.REFERENCED_TABLE_NAME, i1.REFERENCED_COLUMN_NAME,
    i2.UPDATE_RULE, i2.DELETE_RULE 
    FROM   
    information_schema.KEY_COLUMN_USAGE AS i1  
    INNER JOIN 
    information_schema.REFERENTIAL_CONSTRAINTS AS i2 
    ON i1.CONSTRAINT_NAME = i2.CONSTRAINT_NAME 
    WHERE i1.REFERENCED_TABLE_NAME IS NOT NULL  
    AND  i1.TABLE_SCHEMA  ='db_name';

限制到表中的特定列

AND i1.table_name = 'target_tb_name' AND i1.column_name = 'target_col_name'