diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 492859f56b..2bfec9272e 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -45,10 +45,10 @@
class="parameter">c2 + 5, 0)
- IFNULL(input,non-NULL substitute)
- non-NULL
- return second argument if first is NULL
- IFNULL(c1, 'N/A')
+ NULLIF(input,value)
+ input or NULL
+ return NULL if input = value
+ NULLIF(c1, 'N/A')
CASE WHEN expr THEN expr [...] ELSE expr END