Question

我想精确地复制MySql返回有关FK的信息的方式，这些信息是从Information_schema表中提取信息的。

我在MySql上有这些表：

create table test.subjects (
  ID_SUBJECT bigint NOT NULL AUTO_INCREMENT,
  FULL_NAME varchar(200) NOT NULL,
  PRIMARY KEY (ID_SUBJECT)
);

create table test.request_state (   
  ID_REQUEST_STATE char(3) NOT NULL,  
  DESCRIPTION varchar(80) NOT NULL,
  PRIMARY KEY (ID_REQUEST_STATE)
);

create table test.subject_profiles (    
  ID_SUBJECT_PROFILES bigint NOT NULL AUTO_INCREMENT,
  ID_SUBJECT bigint NOT NULL,
  ID_PROFILE bigint,    
  PRIMARY KEY (ID_SUBJECT_PROFILES)
);

CREATE UNIQUE INDEX subject_profiles_uq1
ON test.subject_profiles (ID_SUBJECT, ID_PROFILE);

ALTER TABLE test.subject_profiles add  
  CONSTRAINT subject_profiles_fk1
    foreign key (ID_SUBJECT) 
    REFERENCES test.subjects (ID_SUBJECT) on delete cascade;

create table test.demand (  
  ID_DEMAND bigint NOT NULL AUTO_INCREMENT,
  ID_SUBJECT bigint NOT NULL,
  DEMAND_STATE char(3) not null,
  ID_PROFILE bigint,                          
  PRIMARY KEY (ID_DEMAND)
);

ALTER TABLE test.demand add
  CONSTRAINT demand_fk1
    foreign key (ID_SUBJECT) 
    REFERENCES test.subjects (ID_SUBJECT) on delete cascade;

ALTER TABLE test.demand add
  CONSTRAINT demand_fk2 foreign key (DEMAND_STATE) REFERENCES test.request_state (ID_REQUEST_STATE);                                                       
alter table test.demand
 add CONSTRAINT demand_fk3
    foreign key (ID_SUBJECT, ID_PROFILE) 
    REFERENCES test.subject_profiles (ID_SUBJECT, ID_PROFILE);

及其在Postgresql上的副本：

create table test.subjects (
  ID_SUBJECT bigint NOT NULL,
  FULL_NAME varchar(200) NOT NULL,
  PRIMARY KEY (ID_SUBJECT)
);

create table test.request_state (   
  ID_REQUEST_STATE char(3) NOT NULL,  
  DESCRIPTION varchar(80) NOT NULL,
  PRIMARY KEY (ID_REQUEST_STATE)
);

create table test.subject_profiles (    
  ID_SUBJECT_PROFILES bigint NOT NULL,
  ID_SUBJECT bigint NOT NULL,
  ID_PROFILE bigint,    
  PRIMARY KEY (ID_SUBJECT_PROFILES)
);

CREATE UNIQUE INDEX subject_profiles_uq1
ON test.subject_profiles (ID_SUBJECT, ID_PROFILE);

ALTER TABLE test.subject_profiles add  
  CONSTRAINT subject_profiles_fk1
    foreign key (ID_SUBJECT) 
    REFERENCES test.subjects (ID_SUBJECT) on delete cascade;

create table test.demand (  
  ID_DEMAND bigint NOT NULL,
  ID_SUBJECT bigint NOT NULL,
  DEMAND_STATE char(3) not null,
  ID_PROFILE  bigint,
   PRIMARY KEY (ID_DEMAND)
);

ALTER TABLE test.demand add
  CONSTRAINT demand_fk1
    foreign key (ID_SUBJECT) 
    REFERENCES test.subjects (ID_SUBJECT) on delete cascade;

ALTER TABLE test.demand add
  CONSTRAINT demand_fk2
    foreign key (DEMAND_STATE) REFERENCES test.request_state (ID_REQUEST_STATE);                                                       
alter table test.demand
 add CONSTRAINT demand_fk3
    foreign key (ID_SUBJECT, ID_PROFILE) 
    REFERENCES test.subject_profiles (ID_SUBJECT, ID_PROFILE);

现在，在MySql上进行以下查询：

SELECT 
  CONCAT(table_name) AS table_name, CONCAT(column_name) AS column_name,
  CONCAT(referenced_table_name) AS referenced_table_name,
  CONCAT(referenced_column_name) AS referenced_column_name
FROM 
  INFORMATION_SCHEMA.key_column_usage 
WHERE 
  referenced_table_schema = 'subjects_data'
  and referenced_table_name IS NOT NULL 
  and table_name = 'demand'
ORDER BY table_name, column_name

返回：

table_name  column_name  referenced_table_name referenced_column_name                              
---------------------------------------------------------------------
demand      DEMAND_STATE request_state         ID_REQUEST_STATE                                    
demand      ID_PROFILE   subject_profiles      ID_PROFILE                                          
demand      ID_SUBJECT   subjects              ID_SUBJECT                                          
demand      ID_SUBJECT   subject_profiles      ID_SUBJECT

这是我最好的Postgres“副本”：

SELECT  
  tc.table_name,
  kcu.column_name,
  ccu.table_name as references_table,
  ccu.column_name as references_field
FROM 
  information_schema.table_constraints tc
  LEFT JOIN information_schema.key_column_usage kcu
  ON tc.constraint_catalog = kcu.constraint_catalog
  AND tc.constraint_schema = kcu.constraint_schema
  AND tc.constraint_name = kcu.constraint_name
  LEFT JOIN information_schema.referential_constraints rc
  ON tc.constraint_catalog = rc.constraint_catalog
  AND tc.constraint_schema = rc.constraint_schema
  AND tc.constraint_name = rc.constraint_name
  LEFT JOIN information_schema.constraint_column_usage ccu
  ON rc.unique_constraint_catalog = ccu.constraint_catalog
  AND rc.unique_constraint_schema = ccu.constraint_schema
  AND rc.unique_constraint_name = ccu.constraint_name
WHERE 
  tc.constraint_catalog = 'subjects_db'
  and tc.constraint_schema = 'test' 
  and tc.table_name = 'demand'
  and tc.constraint_type = 'FOREIGN KEY'

返回：

table_name  column_name  referenced_table_name referenced_column_name
---------------------------------------------------------------------
demand      id_subject   subjects              id_subject            
demand      demand_state request_state         id_request_state      
demand      id_subject   <null>                <null>                
demand      id_profile   <null>                <null>

那么，最后，我应该以哪种方式重写Postgres查询，以便检索有关所引用表和列的所有信息？

我相信我缺少一些东西，因为Postgresql结果集中有一些空值。

TIA！

Answer 1

您正在为subject_profiles_uq1使用唯一索引而不是唯一约束。相当多的RDBMS支持此类索引，这些索引通常不在字典视图中以普通方式列出。例如，当您在PostgreSQL数据库上运行此查询时：

SELECT constraint_name, unique_constraint_name
FROM information_schema.referential_constraints;

您应该得到这样的东西：

|       constraint_name | unique_constraint_name |
|-----------------------|------------------------|
| deferred_17_aba21_ref |    deferred_check_pkey |
|  subject_profiles_fk1 |          subjects_pkey |
|            demand_fk1 |          subjects_pkey |
|            demand_fk2 |     request_state_pkey |
|            demand_fk3 |                 (null) |

理想情况下，您不应使用唯一索引，而应使用唯一约束。即像这样定义subject_profiles_uq1：

ALTER TABLE test.subject_profiles
  ADD CONSTRAINT subject_profiles_uq1
    UNIQUE (id_subject, id_profile);

在这种情况下您的查询将起作用。 SQL Fiddle here，产生：

| table_name |  column_name | references_table | references_field |
|------------|--------------|------------------|------------------|
|     demand |   id_subject |         subjects |       id_subject |
|     demand | demand_state |    request_state | id_request_state |
|     demand |   id_subject | subject_profiles |       id_profile |
|     demand |   id_subject | subject_profiles |       id_subject |
|     demand |   id_profile | subject_profiles |       id_profile |
|     demand |   id_profile | subject_profiles |       id_subject |

如果您绝对需要使用唯一索引，则必须查询pg_catalog：

SELECT fc.relname, fa.attname, uc.relname, ua.attname
FROM pg_catalog.pg_constraint f
JOIN pg_namespace fn ON f.connamespace = fn.oid
JOIN pg_catalog.pg_class fc ON f.conrelid = fc.oid
JOIN pg_attribute fa ON fa.attrelid = fc.oid AND fa.attnum = ANY(f.conkey)
JOIN pg_catalog.pg_class uc ON f.confrelid = uc.oid
JOIN pg_attribute ua ON ua.attrelid = uc.oid AND ua.attnum = ANY(f.confkey)
WHERE f.contype = 'f'
AND fc.table_name = 'demand'
AND fn.nspname = 'test'

关于jOOQ

您用jooq标记了您的问题，所以我假设您正在调试jOOQ 3.11的此限制，该限制当前未将唯一索引作为唯一约束：https://github.com/jOOQ/jOOQ/issues/8286

如何从Postgresql检索外键信息

1 个答案:

关于jOOQ