Sqlite primary key on multiple columns

Solution 1:

According to the documentation, it's

CREATE TABLE something (
  column1, 
  column2, 
  column3, 
  PRIMARY KEY (column1, column2)
);

Solution 2:

CREATE TABLE something (
  column1 INTEGER NOT NULL,
  column2 INTEGER NOT NULL,
  value,
  PRIMARY KEY ( column1, column2)
);

Solution 3:

Yes. But remember that such primary key allow NULL values in both columns multiple times.

Create a table as such:

    sqlite> CREATE TABLE something (
column1, column2, value, PRIMARY KEY (column1, column2));

Now this works without any warning:

sqlite> insert into something (value) VALUES ('bla-bla');
sqlite> insert into something (value) VALUES ('bla-bla');
sqlite> select * from something;
NULL|NULL|bla-bla
NULL|NULL|bla-bla

Solution 4:

Basic :

CREATE TABLE table1 (
    columnA INTEGER NOT NULL,
    columnB INTEGER NOT NULL,
    PRIMARY KEY (columnA, columnB)
);

If your columns are foreign keys of other tables (common case) :

CREATE TABLE table1 (
    table2_id INTEGER NOT NULL,
    table3_id INTEGER NOT NULL,
    FOREIGN KEY (table2_id) REFERENCES table2(id),
    FOREIGN KEY (table3_id) REFERENCES table3(id),
    PRIMARY KEY (table2_id, table3_id)
);

CREATE TABLE table2 (
    id INTEGER NOT NULL,
    PRIMARY KEY id
);

CREATE TABLE table3 (
    id INTEGER NOT NULL,
    PRIMARY KEY id
);

Solution 5:

Primary key fields should be declared as not null (this is non standard as the definition of a primary key is that it must be unique and not null). But below is a good practice for all multi-column primary keys in any DBMS.

create table foo
(
  fooint integer not null
  ,foobar string not null
  ,fooval real
  ,primary key (fooint, foobar)
)
;