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DROP TABLE IF EXISTS t1,t2,t3;
CREATE TABLE t1 (id INT NOT NULL, PRIMARY KEY (id)) ENGINE=INNODB;
CREATE TABLE t2 (id INT PRIMARY KEY, t1_id INT, INDEX par_ind (t1_id, id),
FOREIGN KEY (t1_id) REFERENCES t1(id) ON DELETE CASCADE,
FOREIGN KEY (t1_id) REFERENCES t1(id) ON UPDATE CASCADE) ENGINE=INNODB;
CREATE TABLE t3 (id INT PRIMARY KEY, t2_id INT, INDEX par_ind (t2_id),
FOREIGN KEY (id, t2_id) REFERENCES t2(t1_id, id) ON DELETE CASCADE) ENGINE=INNODB;
select * from information_schema.TABLE_CONSTRAINTS where
TABLE_SCHEMA= "test";
CONSTRAINT_CATALOG CONSTRAINT_SCHEMA CONSTRAINT_NAME TABLE_SCHEMA TABLE_NAME CONSTRAINT_TYPE
def test PRIMARY test t1 PRIMARY KEY
def test PRIMARY test t2 PRIMARY KEY
def test t2_ibfk_1 test t2 FOREIGN KEY
def test t2_ibfk_2 test t2 FOREIGN KEY
def test PRIMARY test t3 PRIMARY KEY
def test t3_ibfk_1 test t3 FOREIGN KEY
select * from information_schema.KEY_COLUMN_USAGE where
TABLE_SCHEMA= "test";
CONSTRAINT_CATALOG CONSTRAINT_SCHEMA CONSTRAINT_NAME TABLE_CATALOG TABLE_SCHEMA TABLE_NAME COLUMN_NAME ORDINAL_POSITION POSITION_IN_UNIQUE_CONSTRAINT REFERENCED_TABLE_SCHEMA REFERENCED_TABLE_NAME REFERENCED_COLUMN_NAME
def test PRIMARY def test t1 id 1 NULL NULL NULL NULL
def test PRIMARY def test t2 id 1 NULL NULL NULL NULL
def test t2_ibfk_1 def test t2 t1_id 1 1 test t1 id
def test t2_ibfk_2 def test t2 t1_id 1 1 test t1 id
def test PRIMARY def test t3 id 1 NULL NULL NULL NULL
def test t3_ibfk_1 def test t3 id 1 1 test t2 t1_id
def test t3_ibfk_1 def test t3 t2_id 2 2 test t2 id
drop table t3, t2, t1;
CREATE TABLE t1(a1 INT NOT NULL, a2 INT NOT NULL,
PRIMARY KEY(a1, a2)) ENGINE=INNODB;
CREATE TABLE t2(b1 INT, b2 INT, INDEX (b1, b2),
CONSTRAINT A1
FOREIGN KEY (b1, b2) REFERENCES t1(a1, a2)
ON UPDATE CASCADE ON DELETE NO ACTION) ENGINE=INNODB;
CREATE TABLE t3(b1 INT, b2 INT, INDEX t3_indx (b1, b2),
CONSTRAINT A2
FOREIGN KEY (b1, b2) REFERENCES t2(b1, b2)
ON UPDATE SET NULL ON DELETE RESTRICT) ENGINE=INNODB;
CREATE TABLE t4(b1 INT, b2 INT, UNIQUE KEY t4_ukey (b1, b2),
CONSTRAINT A3
FOREIGN KEY (b1, b2) REFERENCES t3(b1, b2)
ON UPDATE NO ACTION ON DELETE SET NULL) ENGINE=INNODB;
CREATE TABLE t5(b1 INT, b2 INT, INDEX (b1, b2),
CONSTRAINT A4
FOREIGN KEY (b1, b2) REFERENCES t4(b1, b2)
ON UPDATE RESTRICT ON DELETE CASCADE) ENGINE=INNODB;
select a.CONSTRAINT_SCHEMA, b.TABLE_NAME, CONSTRAINT_TYPE,
b.CONSTRAINT_NAME, UNIQUE_CONSTRAINT_SCHEMA, UNIQUE_CONSTRAINT_NAME,
MATCH_OPTION, UPDATE_RULE, DELETE_RULE, b.REFERENCED_TABLE_NAME
from information_schema.TABLE_CONSTRAINTS a,
information_schema.REFERENTIAL_CONSTRAINTS b
where a.CONSTRAINT_SCHEMA = 'test' and a.CONSTRAINT_SCHEMA = b.CONSTRAINT_SCHEMA and
a.CONSTRAINT_NAME = b.CONSTRAINT_NAME;
CONSTRAINT_SCHEMA TABLE_NAME CONSTRAINT_TYPE CONSTRAINT_NAME UNIQUE_CONSTRAINT_SCHEMA UNIQUE_CONSTRAINT_NAME MATCH_OPTION UPDATE_RULE DELETE_RULE REFERENCED_TABLE_NAME
test t2 FOREIGN KEY A1 test PRIMARY NONE CASCADE NO ACTION t1
test t3 FOREIGN KEY A2 test b1 NONE SET NULL RESTRICT t2
test t4 FOREIGN KEY A3 test t3_indx NONE NO ACTION SET NULL t3
test t5 FOREIGN KEY A4 test t4_ukey NONE RESTRICT CASCADE t4
drop tables t5, t4, t3, t2, t1;
create database `db-1`;
use `db-1`;
create table `t-2` (
id int(10) unsigned not null auto_increment,
primary key (id)
) engine=innodb;
create table `t-1` (
id int(10) unsigned not null auto_increment,
idtype int(10) unsigned not null,
primary key (id),
key fk_t1_1 (idtype),
constraint fk_t1_1 foreign key (idtype) references `t-2` (id)
) engine=innodb;
use test;
select referenced_table_schema, referenced_table_name
from information_schema.key_column_usage
where constraint_schema = 'db-1';
referenced_table_schema referenced_table_name
NULL NULL
db-1 t-2
NULL NULL
drop database `db-1`;
create table t1(id int primary key) engine = Innodb;
create table t2(pid int, foreign key (pid) references t1(id)) engine = Innodb;
set foreign_key_checks = 0;
drop table t1;
select UNIQUE_CONSTRAINT_NAME
from information_schema.referential_constraints
where constraint_schema = schema();
UNIQUE_CONSTRAINT_NAME
NULL
drop table t2;
set foreign_key_checks = 1;
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