title: Can I use VARCHAR as the PRIMARY KEY?
body: <p>I have a table for storing coupons/discounts, and I want to use the coupon_code column as the primary key, which is a <code>VARCHAR</code>.</p>
  
  <p>My rationale is that, each coupon will have a unique code, and the only commands I will be running are <code>SELECT ... FROM ... WHERE coupon_code='..'</code></p>
  
  <p>I won't be doing any joins or indexing, and I don't see there ever being more than a few hundred entries in this table.</p>
  
  <p>It seems to me that this will be OK, but I don't know if there is anything I'm missing/not thinking about.</p>