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<计算机技术网(www.ctvol.com)!!>。如有错误或未考虑完全的地方，望不吝赐教。
需要了解更多数据库技术:Postgresql 查询表引用或被引用的外键操作，都可以关注数据库技术分享栏目—计算机技术网(www.ctvol.com)!
本文来自网络收集，不代表计算机技术网立场，如涉及侵权请联系管理员删除。
ctvol管理联系方式QQ:251552304
本文章地址：https://www.ctvol.com/dtteaching/632706.html