diff --git a/mysql/functions.go b/mysql/functions.go
index 2a8e227..24cd73c 100644
--- a/mysql/functions.go
+++ b/mysql/functions.go
@@ -261,10 +261,22 @@ func UNIX_TIMESTAMP(str StringExpression) TimestampExpression {
 	return jet.NewTimestampFunc("UNIX_TIMESTAMP", str)
 }
 
-//----------- Comparison operators ---------------//
+// --------------- Conditional Expressions Functions -------------//
 
 // EXISTS checks for existence of the rows in subQuery
 var EXISTS = jet.EXISTS
 
 // CASE create CASE operator with optional list of expressions
 var CASE = jet.CASE
+
+// COALESCE function returns the first of its arguments that is not null.
+var COALESCE = jet.COALESCE
+
+// NULLIF function returns a null value if value1 equals value2; otherwise it returns value1.
+var NULLIF = jet.NULLIF
+
+// GREATEST selects the largest value from a list of expressions, or null if any of the expressions is null.
+var GREATEST = jet.GREATEST
+
+// LEAST selects the smallest value from a list of expressions, or null if any of the expressions is null.
+var LEAST = jet.LEAST
diff --git a/postgres/literal.go b/postgres/literal.go
index 7b1bd19..e3a95b3 100644
--- a/postgres/literal.go
+++ b/postgres/literal.go
@@ -65,6 +65,16 @@ func String(value string) StringExpression {
 	return CAST(jet.String(value)).AS_TEXT()
 }
 
+// Json creates new json literal expression
+func Json(value interface{}) StringExpression {
+	switch value.(type) {
+	case string, []byte:
+	default:
+		panic("Bytea parameter value has to be of the type string or []byte")
+	}
+	return StringExp(CAST(jet.Literal(value)).AS("json"))
+}
+
 // UUID is a helper function to create string literal expression from uuid object
 // value can be any uuid type with a String method
 var UUID = jet.UUID
diff --git a/postgres/literal_test.go b/postgres/literal_test.go
index 5c5160e..9fef055 100644
--- a/postgres/literal_test.go
+++ b/postgres/literal_test.go
@@ -67,6 +67,11 @@ func TestBytea(t *testing.T) {
 	assertSerialize(t, Bytea([]byte("Some byte array")), `$1::bytea`, []byte("Some byte array"))
 }
 
+func TestJson(t *testing.T) {
+	assertSerialize(t, Json("{\"key\": \"value\"}"), `$1::json`, "{\"key\": \"value\"}")
+	assertSerialize(t, Json([]byte("{\"key\": \"value\"}")), `$1::json`, []byte("{\"key\": \"value\"}"))
+}
+
 func TestDate(t *testing.T) {
 	assertSerialize(t, Date(2014, time.January, 2), `$1::date`, "2014-01-02")
 	assertSerialize(t, DateT(time.Now()), `$1::date`)