How to Fix Query Error in Clojure

Few things halt development faster than an unexpected query error in Clojure. The good news is this is a well-understood problem with a clear solution. Let's get you back on track.

Common Causes

Query errors in Clojure usually stem from one of these issues:

• Malformed SQL syntax or incorrect query builder usage
• Missing, null, or incorrectly typed parameters
• Type mismatches between query parameters and database column types
• Attempting to access results from an empty result set
• Connection pool exhaustion under high load

The Fix

(require '[next.jdbc :as jdbc])
(require '[next.jdbc.result-set :as rs])

;; Parameterized query — safe from injection
(let [user (jdbc/execute-one! ds
              ["SELECT * FROM users WHERE id = ?" user-id]
              {:builder-fn rs/as-unqualified-lower-maps})]
  (if user
    user
    (throw (ex-info "User not found" {:user-id user-id}))))

next.jdbc handles parameterization automatically with the vector syntax. Use execute-one! for single-row queries.

Preventing Query Errors

• Use an ORM or query builder to reduce raw SQL mistakes and prevent injection
• Validate input types before passing them to queries
• Handle empty results explicitly rather than assuming data always exists
• Log the full query text (without sensitive data) when errors occur for debugging
• Monitor slow queries to catch performance issues before they become errors

Let [Bugsly](https://bugsly.dev) capture and group query errors in your Clojure app so you can see exactly which queries are failing, how often, and with what parameters.