Question

I am using a table to store votes of different users on different polls.

Table has following structure.

id   |  poll_id  |   opt   |  ip_address

id : auto increment

poll_id : (STRING UNIQUE) unique for a particular poll  

opt : (STRING) option selected by user    

ip_address: (STRING UNIQUE) ip address of user

This is my query

INSERT OR REPLACE INTO tbl_poll(id,poll_id,opt,ip_addr) VALUES (null,'$poll_id','$opt','$ip_addr')

(Here $poll_id, $opt and $ip_addr are php variables which holds the respective values)

Now, the scenario is like this,

User ‘A’ votes for option 2 of poll_id ‘mypoll’. Query works perfectly. (Does insert)

User ‘A’ changes mind and votes for option 5 of poll_id ‘mypoll’. Query works perfectly. (Does replace)

But if User ‘A’ votes for option 4 of poll_id ‘yourpoll’. Query fails (It does a replace) but it should insert a new record with poll_id ‘yourpoll’

I think, it considers the unqiue constraint of ip_address only but not the poll_id

Answer 1

From your description on the desired functionality, it would seem that you want poll_id and ip_address to be a unique pair or compound unique.

CREATE TABLE tbl_poll ( 
    id         INTEGER PRIMARY KEY AUTOINCREMENT,
    poll_id    STRING NOT NULL,
    ip_address STRING NOT NULL,
    opt        STRING NULL,
    CONSTRAINT 'unique_vote_per_poll_per_ip_address' UNIQUE ( poll_id, ip_address )  ON CONFLICT REPLACE 
);