Newbie question on database efficiency
Knowing everything you have specified, I suggest you to create this model:

/********Characters********
this is the table where all the players exist
*/
CREATE TABLE characters (
    id      &lt;id_type&gt; NOT NULL,
    name    &lt;column_type&gt; ,
    other   &lt;column_type&gt;  
);
ALTER TABLE characters ADD CONSTRAINT c_pk PRIMARY KEY ( id );

/********Item Type********
this is the type of item; i.e. poison, sword,...
*/
CREATE TABLE item_type (
    id      &lt;id_type&gt; NOT NULL,
    name    &lt;column_type&gt;,
    other   &lt;column_type&gt; 
);
ALTER TABLE item_type ADD CONSTRAINT t_pk PRIMARY KEY ( id );

/********Items********
this is every single and unique existence of any item in the game...
*/
CREATE TABLE items (
    id       &lt;id_type&gt; NOT NULL,
    typeid   &lt;id_type&gt; NOT NULL,
    other    &lt;column_type&gt; 
);
ALTER TABLE items ADD CONSTRAINT i_pk PRIMARY KEY ( id );
ALTER TABLE items ADD CONSTRAINT i_t_fk FOREIGN KEY ( typeid ) REFERENCES item_type ( id );

/********Inventory********
this relates all players with all of their items
*/
CREATE TABLE inventory (
    characterid   &lt;id_type&gt; NOT NULL,
    itemid        &lt;id_type&gt; NOT NULL
);
ALTER TABLE inventory ADD CONSTRAINT in_pk PRIMARY KEY ( characterid, itemid );
ALTER TABLE inventory ADD CONSTRAINT in_c_fk FOREIGN KEY ( characterid ) REFERENCES characters ( id );
ALTER TABLE inventory ADD CONSTRAINT in_i_fk FOREIGN KEY ( itemid ) REFERENCES items ( id );


I hope this solution helps you to better approach what you are looking for your game.