Sqlite primary key on multiple columns

Question

What is the syntax for specifying a primary key on more than 1 column in SQLITE ?

Answer 1

According to the documentation, it's

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

Answer 2

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

Answer 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

Answer 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
);

Answer 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)
)
;

Answer 6

Since version 3.8.2 of SQLite, an alternative to explicit NOT NULL specifications is the "WITHOUT ROWID" specification: [1]

NOT NULL is enforced on every column of the PRIMARY KEY
in a WITHOUT ROWID table.

"WITHOUT ROWID" tables have potential efficiency advantages, so a less verbose alternative to consider is:

CREATE TABLE t (
  c1, 
  c2, 
  c3, 
  PRIMARY KEY (c1, c2)
 ) WITHOUT ROWID;

For example, at the sqlite3 prompt: sqlite> insert into t values(1,null,3); Error: NOT NULL constraint failed: t.c2

Answer 7

In another way, you can also make the two column primary key unique and the auto-increment key primary. Just like this: https://stackoverflow.com/a/6157337

Answer 8

The following code creates a table with 2 column as a primary key in SQLite.

SOLUTION:

CREATE TABLE IF NOT EXISTS users (id TEXT NOT NULL, name TEXT NOT NULL, pet_name TEXT, PRIMARY KEY (id, name))

Answer 9

PRIMARY KEY (id, name) didn't work for me. Adding a constraint did the job for me.

CREATE TABLE IF NOT EXISTS customer (id INTEGER, name TEXT, user INTEGER, CONSTRAINT PK_CUSTOMER PRIMARY KEY (user, id))