diff --git a/library/think/db/Builder.php b/library/think/db/Builder.php
index 66c5b389..a9b5b143 100644
--- a/library/think/db/Builder.php
+++ b/library/think/db/Builder.php
@@ -26,7 +26,7 @@ abstract class Builder
     protected $exp = ['eq' => '=', 'neq' => '<>', 'gt' => '>', 'egt' => '>=', 'lt' => '<', 'elt' => '<=', 'notlike' => 'NOT LIKE', 'not like' => 'NOT LIKE', 'like' => 'LIKE', 'in' => 'IN', 'exp' => 'EXP', 'notin' => 'NOT IN', 'not in' => 'NOT IN', 'between' => 'BETWEEN', 'not between' => 'NOT BETWEEN', 'notbetween' => 'NOT BETWEEN', 'exists' => 'EXISTS', 'notexists' => 'NOT EXISTS', 'not exists' => 'NOT EXISTS', 'null' => 'NULL', 'notnull' => 'NOT NULL', 'not null' => 'NOT NULL', '> time' => '> TIME', '< time' => '< TIME', '>= time' => '>= TIME', '<= time' => '<= TIME', 'between time' => 'BETWEEN TIME', 'not between time' => 'NOT BETWEEN TIME', 'notbetween time' => 'NOT BETWEEN TIME'];
 
     // SQL表达式
-    protected $selectSql    = 'SELECT%DISTINCT% %FIELD% FROM %TABLE%%FORCE%%UNION%%JOIN%%WHERE%%GROUP%%HAVING%%ORDER%%LIMIT%%LOCK%%COMMENT%';
+    protected $selectSql    = 'SELECT%DISTINCT% %FIELD% FROM %TABLE%%FORCE%%JOIN%%WHERE%%GROUP%%HAVING%%UNION%%ORDER%%LIMIT%%LOCK%%COMMENT%';
     protected $insertSql    = '%INSERT% INTO %TABLE% (%FIELD%) VALUES (%DATA%) %COMMENT%';
     protected $insertAllSql = '%INSERT% INTO %TABLE% (%FIELD%) %DATA% %COMMENT%';
     protected $updateSql    = 'UPDATE %TABLE% SET %SET% %JOIN% %WHERE% %ORDER%%LIMIT% %LOCK%%COMMENT%';