MySQL: how can I see ALL constraints on a table? -

i'm learning sql , bothers me, seem unable find constraints on table. created table with

create table t2 (a integer not null primary key, b integer not null, constraint c1 check(b>0), constraint fk1 foreign key(a) references t1(a));

and added constraint with

alter table t2 add constraint c2 check (b<20);

i tried see (four) constraints with

show table status tenn #-->the name of database 't2';

and then

show create table t2;

and then

select * information_schema.key_column_usage table_name='t2';

and finally

select * information_schema.table_constraints table_name='t2';

but none of these shows 4 constraints. tell me how see of them?

thanks lot!

select column_name, constraint_name, referenced_column_name, referenced_table_name information_schema.key_column_usage table_name = 'table checked';

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