How do I set a joint primary key in Oracle?

Set this parameter when you create a table.

create table tab (

ID1 NUMBER(10), ID2 NUMBER(4), CREDIT NUMBER(2), Constraint PK TAB Primary Key (ID1, ID2) - Primary key.

Or add it after the table is created.

alter table tab add constraint pk_tab2 primary key (id1,id2);

You are talking about the problem of a single primary key and a joint primary key, a table can only have one primary key: a column-based primary key: alter table test add constraint pk test primary key(ename); Multi-column-based union primary key:

alter table test add constraint pk_test primary key(ename,birthday);

Set this parameter when you create a table.

create table tab

id1 number(10)

ID2 number(4),credit number(2),constraint pk tab primary key ID1,ID2) primary key.

Or add it after the table is created.

alter table tab add constraint pk_tab2 primary key (id1,id2);

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Composite primary key: constraints pk relation primary key(dept id, staff id).

Constraints fk c r a composite foreign key(dept id,staff id) references t relation(dept id,staff id).

I agree with the statement on the second floor, generally do not write like this, unless there is a special business need hibernate composite primary key configuration:

This is easier to use, and you don't need to match it with many to many.

I tried the compound foreign key, but I couldn't get it. I don't know if I didn't write it correctly or if I didn't support it in the first place.

Create a grade sheet T Grade, and set the Student ID S ID + Course ID C ID as the composite primary key.

create table t grade ( - Student grade sheet.

s id number(8), student number.

c id number(4), course code.

g ps varchar2(6), usual grades.

g ks varchar2(6), test results.

constraint grade_pk primary key (s_id,c_id));Table-level composite primary key.

You can set a composite foreign key. The method is the same as the composite primary key, primary key(...)Into.

foreign key(..references main table (...)

or alter table add constraint foreign key name.

foreign key references Primary table (primary key|unique key);

create table table name (.

a ..b...constraint primary key(a,b)); If the table has already been created, add alter table table name add constraint primary key(a,b);

When defining a table, the field only needs to define the data type and length, and then add constraints at the end, similar to: constraint pk 1 primary key(*,

At the end of the table statement, add primary key(c1,c2).

Set this parameter when you create a table.

create table tab (

ID1 NUMBER(10), ID2 NUMBER(4), CREDIT NUMBER(2), Constraint PK TAB Primary Key (ID1, ID2) - Primary key.

Or add it after the table is created.

alter table tab add constraint pk_tab2 primary key (id1,id2);

The union primary key is simply the fields that make the record union unique, such as id1 id2 id3

There can be 2 id 1s, but there is certainly only one 1 0 0.

The query should also come as needed, write an equivalent query:

select a.*,from tab1 a,tab2 b where and and ;

As for other restrictions such as month, let's search for your own needs.

If you want to get the results of this kind of query you want, you can use the external query.

select * from tablename1 full join tablename2 on ;