码:
create table coltype (coltype varchar(5));
insert into coltype values ('typ1');
create table colsubtype (coltype varchar(5), colsubtype varchar(5));
insert into colsubtype values ('typ2', 'st1');
insert into colsubtype values ('typ2', 'st2');
create table table1 (col1 varchar(5), coltype varchar(5), colsubtype varchar(5));
insert into table1 values ('val1','typ1', 'st1');
insert into table1 values ('val2','typ1', 'st2');
insert into table1 values ('val3','typ1', 'st3');
insert into table1 values ('val4','typ2', 'st1');
insert into table1 values ('val5','typ2', 'st2');
insert into table1 values ('val6','typ2', 'st3');
insert into table1 values ('val7','typ3', …Run Code Online (Sandbox Code Playgroud)