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)

示例：

以上为个人经验，希望能给大家一个参考，也希望大家多多支持。如有错误或未考虑完全的地方，望不吝赐教。