Metabase -- Marginalia

metabase.driver.sql.query-processor.empty-string-is-null toc
In Oracle and some other databases, empty strings are considered to be `NULL`, so `WHERE field = ''` is effectively the same as writing `WHERE field = NULL`, which of course is never true. This impl replaces empty-string values with `nil` so we generate correct SQL e.g. `WHERE field IS NOT NULL`. (See #13158) Drivers can derive from this abstract driver to use an alternate implementation(s) of SQL QP method(s) that treat empty strings as `nil`.	(ns metabase.driver.sql.query-processor.empty-string-is-null (:require [metabase.driver :as driver] [metabase.driver.sql.query-processor :as sql.qp]))
	(driver/register! ::empty-string-is-null, :abstract? true)
	(defmethod sql.qp/->honeysql [::empty-string-is-null :value] [driver [_ value info]] (let [value (when-not (= value "") value)] ((get-method sql.qp/->honeysql [:sql :value]) driver [:value value info])))
	(prefer-method sql.qp/->honeysql [::empty-string-is-null :value] [:sql :value])

metabase.driver.sql.query-processor.empty-string-is-null