如何在PostgreSQL服务器中查看表关系？

  - 查看表之间的外键关系：

    ```sql

    SELECT conname AS constraint_name, conrelid::regclass AS table_name, a.attname AS column_name,

           confrelid::regclass AS foreign_table_name, af.attname AS foreign_column_name

    FROM pg_constraint c

    JOIN pg_class cl ON c.conrelid = cl.oid

    JOIN pg_attribute a ON a.attnum = ANY(c.conkey) AND a.attrelid = cl.oid

    JOIN pg_class clf ON c.confrelid = clf.oid

    JOIN pg_attribute af ON af.attnum = ANY(c.confkey) AND af.attrelid = clf.oid

    WHERE contype = 'f';

    ```

  - 查看表之间的引用关系：

    ```sql

    SELECT conname AS constraint_name, conrelid::regclass AS table_name, a.attname AS column_name,

           confrelid::regclass AS referenced_table_name, af.attname AS referenced_column_name

    FROM pg_constraint c

    JOIN pg_class cl ON c.conrelid = cl.oid

    JOIN pg_attribute a ON a.attnum = ANY(c.conkey) AND a.attrelid = cl.oid

    JOIN pg_class clf ON c.confrelid = clf.oid

    JOIN pg_attribute af ON af.attnum = ANY(c.confkey) AND af.attrelid = clf.oid

    WHERE contype = 'f';

    ```

  - 查看表之间的依赖关系：

    ```sql

    SELECT conname AS constraint_name, conrelid::regclass AS table_name, a.attname AS column_name,

           confrelid::regclass AS dependent_table_name, af.attname AS dependent_column_name

    FROM pg_constraint c

    JOIN pg_class cl ON c.conrelid = cl.oid

    JOIN pg_attribute a ON a.attnum = ANY(c.conkey) AND a.attrelid = cl.oid

    JOIN pg_class clf ON c.confrelid = clf.oid

    JOIN pg_attribute af ON af.attnum = ANY(c.confkey) AND af.attrelid = clf.oid

    WHERE contype = 'f';

    ```