Postgresql 查询表引用或被引用的外键操作

今天更新两个SQL。是用来查询PG中，主表被子表引用的外键，或子表引用了哪个主表的主键。

废话不多说，直接上实验！

CentOS 7 + PG 10

创建两个实验表，test01为主表，test02为子表，test02引用test01中的id列。

									test=# create table test01(

									test(# id int primary key,

									test(# col1 varchar(20)

									test(# );

									CREATE TABLE

									test=# create table test02(

									test(# id int primary key,

									test(# test01_id int references test01(id),

									test(# col1 varchar(20)

									test(# );

									CREATE TABLE

插入数据

									test=# insert into test01 values (1, 'a');

									INSERT 0 1

									test=# insert into test01 values (2, 'b');

									INSERT 0 1

									test=# insert into test01 values (3, 'c');

									INSERT 0 1

									test=# insert into test02 values (1, 1, 'a');

									INSERT 0 1

									test=# insert into test02 values (2, 1, 'a');

									INSERT 0 1

									test=# insert into test02 values (3, 1, 'a');

									INSERT 0 1

									test=# insert into test02 values (4, 2, 'b');

									INSERT 0 1

									test=# insert into test02 values (5, 2, 'b');

									INSERT 0 1

									test=# insert into test02 values (6, 11, 'b');

									ERROR: insert or update on table "test02" violates foreign key constraint "test02_test01_id_fkey"

									DETAIL: Key (test01_id)=(11) is not present in table "test01".

查询主表被哪个子表引用。如果结果为空，说明没有任何子表引用的该表。

									test=# SELECT

									tc.constraint_name,

									tc.table_name, # 子表

									kcu.column_name,

									ccu.table_name AS foreign_table_name, # 主表

									ccu.column_name AS foreign_column_name,

									tc.is_deferrable,

									tc.initially_deferred

									FROM

									information_schema.table_constraints AS tc

									JOIN information_schema.key_column_usage AS kcu ON tc.constraint_name = kcu.constraint_name

									JOIN information_schema.constraint_column_usage AS ccu ON ccu.constraint_name = tc.constraint_name

									where constraint_type = 'FOREIGN KEY' AND ccu.table_name='test01'; # 输入主表

									constraint_name | table_name | column_name | foreign_table_name | foreign_column_name | is_deferrable | initially_deferred

									-----------------------+------------+-------------+--------------------+---------------------+---------------+--------------------

									test02_test01_id_fkey | test02 | test01_id | test01 | id | NO | NO

									(1 row)

查询子表引用的哪个主表。如果结果为空，说明没有任何引用主表。

									test=# SELECT

									tc.constraint_name,

									tc.table_name, # 子表

									kcu.column_name,

									ccu.table_name AS foreign_table_name,

									ccu.column_name AS foreign_column_name, # 主表

									tc.is_deferrable,

									tc.initially_deferred

									FROM

									information_schema.table_constraints AS tc

									JOIN information_schema.key_column_usage AS kcu ON tc.constraint_name = kcu.constraint_name

									JOIN information_schema.constraint_column_usage AS ccu ON ccu.constraint_name = tc.constraint_name

									WHERE constraint_type = 'FOREIGN KEY' AND tc.table_name='test02'; # 输入子表

									constraint_name | table_name | column_name | foreign_table_name | foreign_column_name | is_deferrable | initially_deferred

									-----------------------+------------+-------------+--------------------+---------------------+---------------+--------------------

									test02_test01_id_fkey | test02 | test01_id | test01 | id | NO | NO

									(1 row)

补充：PostgreSQL 外键引用查询

根据一个表名，查询所有外键引用它的表，以及那些外键的列名

key_column_usage（系统列信息表），

pg_constraint（系统所有约束表）

									SELECT x.table_name,

									    x.column_name

									 FROM information_schema.key_column_usage x

									 INNER JOIN (SELECT t.relname, 

									            a.conname 

									         FROM pg_constraint a 

									         INNER JOIN pg_class ft

									             ON ft.oid = a.confrelid 

									         INNER JOIN pg_class t 

									             ON t.oid = a.conrelid

									        WHERE a.contype = 'f'

									         AND a.confrelid =

									            (select e.oid 

									             from pg_class e

									             where e.relname = 'xxx_table')

									        ) tp 

									     ON (x.table_name = tp.relname AND

									       x.constraint_name = tp.conname)