diff --git a/README.markdown b/README.markdown
index 3c16b97..0aa019f 100644
--- a/README.markdown
+++ b/README.markdown
@@ -21,10 +21,10 @@
 ;=> #<SXQL-COMPILED: SELECT id, name, sex FROM person AS p WHERE ((age >= ?) AND (age < ?)) ORDER BY age DESC [18, 65]>
 
 (union-queries * (select (:id :name :sex) (from '(:as animal a))))
-;=> #<SXQL-OP: (SELECT id, name, sex FROM (person AS p) WHERE ((age >= ?) AND (age < ?)) ORDER BY age DESC) UNION (SELECT id, name, sex FROM (animal AS a))>
+;=> #<SXQL-OP: SELECT id, name, sex FROM (person AS p) WHERE ((age >= ?) AND (age < ?)) ORDER BY age DESC UNION SELECT id, name, sex FROM (animal AS a)>
 
 (yield *)
-;=> "(SELECT id, name, sex FROM (person AS p) WHERE ((age >= ?) AND (age < ?)) ORDER BY age DESC) UNION (SELECT id, name, sex FROM (animal AS a))"
+;=> "SELECT id, name, sex FROM (person AS p) WHERE ((age >= ?) AND (age < ?)) ORDER BY age DESC UNION SELECT id, name, sex FROM (animal AS a)"
 ;   (18 65)
 ```
 
@@ -118,7 +118,7 @@ Creates a SELECT query. It takes a field (or a list of fields) and SQL Clauses.
 (union-queries
  (select (:name :birthday) (from :fulltime))
  (select (:name :birthday) (from :parttime)))
-;=> #<SXQL-OP: (SELECT name, birthday FROM fulltime) UNION (SELECT name, birthday FROM parttime)>
+;=> #<SXQL-OP: SELECT name, birthday FROM fulltime UNION SELECT name, birthday FROM parttime>
 ```
 
 ### union-all-queries (&rest statements)
@@ -127,7 +127,7 @@ Creates a SELECT query. It takes a field (or a list of fields) and SQL Clauses.
 (union-all-queries
  (select (:name :birthday) (from :fulltime))
  (select (:name :birthday) (from :parttime)))
-;=> #<SXQL-OP: (SELECT name, birthday FROM fulltime) UNION ALL (SELECT name, birthday FROM parttime)>
+;=> #<SXQL-OP: SELECT name, birthday FROM fulltime UNION ALL SELECT name, birthday FROM parttime>
 ```
 
 ### create-table (table column-definitions &body options)
diff --git a/src/operator.lisp b/src/operator.lisp
index 9634b09..921d0e5 100644
--- a/src/operator.lisp
+++ b/src/operator.lisp
@@ -245,7 +245,7 @@ case letters."
        (format nil (if *inside-select*
                        "(~{~A~^ ~})"
                        "~{~A~^ ~}")
-               (append (list (format nil ,(format nil "~~{(~~A)~~^ ~a ~~}" keyword)
+               (append (list (format nil ,(format nil "~~{~~A~~^ ~a ~~}" keyword)
                                      (mapcar #'yield statements)))
                        (when others
                          (list (format nil "~{~A~^ ~}"
diff --git a/t/operator.lisp b/t/operator.lisp
index 9fff149..7946d33 100644
--- a/t/operator.lisp
+++ b/t/operator.lisp
@@ -249,7 +249,7 @@
                      (select :* (from :table2))
                      (order-by :column1)
                      (limit 1))))
-    (list "(SELECT * FROM `table1`) UNION (SELECT * FROM `table2`) ORDER BY `column1` LIMIT 1"
+    (list "SELECT * FROM `table1` UNION SELECT * FROM `table2` ORDER BY `column1` LIMIT 1"
           nil))
 
 (let ((*inside-select* t))
@@ -259,7 +259,7 @@
                        (select :* (from :table2))
                        (order-by :column1)
                        (limit 1))))
-      (list "((SELECT * FROM `table1`) UNION (SELECT * FROM `table2`) ORDER BY `column1` LIMIT 1)"
+      (list "(SELECT * FROM `table1` UNION SELECT * FROM `table2` ORDER BY `column1` LIMIT 1)"
             nil)))
 
 (is (multiple-value-list
@@ -268,7 +268,7 @@
                      (select :* (from :table2))
                      (order-by :column1)
                      (limit 1))))
-    (list "(SELECT * FROM `table1`) UNION ALL (SELECT * FROM `table2`) ORDER BY `column1` LIMIT 1"
+    (list "SELECT * FROM `table1` UNION ALL SELECT * FROM `table2` ORDER BY `column1` LIMIT 1"
           nil))
 
 (let ((*inside-select* t))
@@ -278,7 +278,7 @@
                        (select :* (from :table2))
                        (order-by :column1)
                        (limit 1))))
-      (list "((SELECT * FROM `table1`) UNION ALL (SELECT * FROM `table2`) ORDER BY `column1` LIMIT 1)"
+      (list "(SELECT * FROM `table1` UNION ALL SELECT * FROM `table2` ORDER BY `column1` LIMIT 1)"
             nil)))
 
 (is (multiple-value-list
diff --git a/t/statement.lisp b/t/statement.lisp
index a39e4fa..425ec4a 100644
--- a/t/statement.lisp
+++ b/t/statement.lisp
@@ -243,6 +243,6 @@
                                                (make-clause :from (make-sql-symbol "table-2"))))))
     (ok union-stmt)
     (is (multiple-value-list (yield union-stmt))
-        '("(SELECT * FROM `table-name` WHERE (`age` < ?)) UNION (SELECT * FROM `table-2`)" (20)))))
+        '("SELECT * FROM `table-name` WHERE (`age` < ?) UNION SELECT * FROM `table-2`" (20)))))
 
 (finalize)
diff --git a/t/sxql.lisp b/t/sxql.lisp
index e8db252..b37900e 100644
--- a/t/sxql.lisp
+++ b/t/sxql.lisp
@@ -202,14 +202,14 @@
 (is-mv (union-queries
         (select :* (from :table-1) (where (:= :a 10)))
         (select :* (from :table-2) (where (:> :b 100))))
-       '("(SELECT * FROM `table-1` WHERE (`a` = ?)) UNION (SELECT * FROM `table-2` WHERE (`b` > ?))"
+       '("SELECT * FROM `table-1` WHERE (`a` = ?) UNION SELECT * FROM `table-2` WHERE (`b` > ?)"
          (10 100))
        "UNION")
 
 (is-mv (union-all-queries
         (select :* (from :table-1) (where (:= :a 10)))
         (select :* (from :table-2) (where (:> :b 100))))
-       '("(SELECT * FROM `table-1` WHERE (`a` = ?)) UNION ALL (SELECT * FROM `table-2` WHERE (`b` > ?))"
+       '("SELECT * FROM `table-1` WHERE (`a` = ?) UNION ALL SELECT * FROM `table-2` WHERE (`b` > ?)"
          (10 100))
        "UNION ALL")