SQL Server : if record found update else insert, merge query error correction

Question

I have come up with following query for SQL Server for updating a row if found else insert

merge tblpermissions  as t
using (select cid, uid from tblpermissions) as s
on (t.cid = s.cid and t.uid=s.uid)
when not matched
THEN INSERT (cid, uid, [read], [write], [readonly], [modify], [admin]) VALUES ('1',   '1', 1, 1, 0, 1, 1) 
when matched 
THEN UPDATE SET [read]=1, write=1, readonly=0, modify=1, admin=1 ;

Although it does not throw any error, its not achieving what I expect. there's no record in the table and its not inserting new record.

Any correction?

Edit: Considering your suggestions I have modified it further as below,without any expected result though -

MERGE INTO tblpermissions  as t
using (SELECT '1' AS cid, '1' AS uid FROM tblpermissions) as s
on (t.cid = s.cid and t.uid=s.uid)
WHEN NOT MATCHED 
THEN INSERT (cid, uid, [read], [write], [readonly], [modify], [admin])
VALUES  ('1', '1', 1, 1, 0, 1, 1) 
WHEN MATCHED
THEN UPDATE SET [read]=1, write=1, readonly=0, modify=1, admin=1 ;

Edit: pls check comment at the bottom, below is the improved query on your suggestions, not to mention it wont work as expected as it takes same table again.

MERGE INTO tblpermissions  as t
using tblpermissions as s
on (t.cid = s.cid and t.uid=s.uid)
WHEN NOT MATCHED 
THEN INSERT (cid, uid, [read], [write], [readonly], [modify], [admin])
VALUES  ('1', '1', 1, 1, 0, 0, 1) 
WHEN MATCHED
THEN UPDATE SET [read]=1, write=1, readonly=0, modify=1, admin=1 ;

Edit: select-if found update-else insert alternative below -

$query = "SELECT * FROM ".SQL_PREFIX."permissions\n"
              ."WHERE cid='".$cid."' AND uid='".$uid."'";
    $sth = $this->dbh->query($query);
    $res = $sth->fetch();
    //print_r($res);var_dump($res);
    if(!$res || $res==null)
    {
        $query = "INSERT INTO ".SQL_PREFIX."permissions (cid, uid, [read], [write], [readonly], [modify], [admin])\n"
            ."VALUES ('$cid', '$uid', ".implode(", ", $values).")";
        if(!($sth = $this->dbh->query($query)))
            $this->db_error(__('Error inserting user permissions.'),
                $query);
    }else{
        $query = "UPDATE ".SQL_PREFIX."permissions SET ".implode(", ", $sets).";";
        if(!($sth = $this->dbh->query($query)))
            $this->db_error(__('Error updating user permissions.'),
                $query);
    } 

Edit: Below is the mysql solution for this situation -

INSERT into tblpermissions (cid, uid, [read], [write], [readonly], [modify], [admin]) VALUES ('1', '1', 1, 1, 0, 0, 1) ON DUPLICATE KEY UPDATE [read]=1, write=1, readonly=0, modify=1, admin=1

which simply employs the keyword DUPLICATE KEY. Also would like to highlight again that, there's unique key constraint on cid & uid combination. So what mysql does is, first it simply looks for the combination of cid & uid we are trying to insert, if found updates it else inserts fresh record.

Answer 1

Because the source and target tables are the same, there is never a case of rows not matching. All rows on the tblpermissions are being updated.

In order to insert, the source table (defined with using ) has to be different from the target table, such as the following examples:

merge tblpermissions  as t
using (select cid, uid from otherTable) as s
on (t.cid = s.cid and t.uid = s.uid)

merge tblpermissions  as t
using (select cid, uid from tblpermissions) as s
on (t.cid = s.cid + 1 and t.uid = s.uid + 1)

Edit: Since you're using constant values instead of the result of a select from any table, maybe the following would do the trick:

merge tblpermissions as t
using (select '1' cid, '1' uid, 1 [read], 1 [write], 0 [readonly], 0 [modify], 1 [admin]) s
on (t.cid = s.cid and t.uid = s.uid)
when matched 
    then update set [read] = s.[read], write = s.[write], readonly = s.[readonly], modify = s.[modify], admin = s.[admin]
when not matched
    then insert (cid, uid, [read], [write], [readonly], [modify], [admin]) values (s.cid, s.uid, s.[read], s.[write], s.[readonly], s.[modify], s.[admin]);

Although I think to insert only one row merge is overkill, it would be easier to do the following:

if exists (select 1 from tblpermissions where cid = '1' and uid = '1')
update tblpermissions set [read] = 1, write = 1, readonly = 0, modify = 1, admin = 1 where cid = '1' and uid = '1'
else
    insert tblpermissions (cid, uid, [read], [write], [readonly], [modify], [admin]) VALUES ('1', '1', 1, 1, 0, 1, 1)

I don't think SQL Server has a shorter or more elegant way to perform this, nothing like on duplicate from MySQL.