diff --git a/SqlBuilder.php b/SqlBuilder.php
index 8159b1b..4a01174 100644
--- a/SqlBuilder.php
+++ b/SqlBuilder.php
@@ -112,13 +112,7 @@ class SqlBuilder extends Component
 			return Kiri::getLogger()->logCategory('None data update.');
 		}
 
-		return join(' ', [
-			'UPDATE',
-			$this->getFromAlias(),
-			'SET',
-			implode(', ', $string),
-			$this->make(),
-		]);
+		return 'UPDATE ' . $this->getFromAlias() . ' ' . 'SET' . ' ' . implode(', ', $string) . ' ' . $this->make();
 	}
 
 
@@ -152,12 +146,9 @@ class SqlBuilder extends Component
 	 */
 	public function delete(): string
 	{
-		return join(' ', [
-			'DELETE',
-			'FROM',
-			$this->getFromAlias(),
-			$this->make(),
-		]);
+		return 'DELETE FROM ' .
+			$this->getFromAlias() . ' ' .
+			$this->make();
 	}
 
 
@@ -231,7 +222,7 @@ class SqlBuilder extends Component
 	 */
 	public function all(): string
 	{
-		return join(' ', [$this->makeSelect($this->query), $this->make(), $this->makeLimit()]);
+		return $this->makeSelect($this->query) . ' ' . $this->make() . ' ' . $this->makeLimit();
 	}
 
 
@@ -241,7 +232,7 @@ class SqlBuilder extends Component
 	 */
 	public function count(): string
 	{
-		return join(' ', [$this->makeSelect(['COUNT(*)']), $this->make()]);
+		return $this->makeSelect(['COUNT(*)']) . ' ' . $this->make();
 	}
 
 
@@ -251,7 +242,7 @@ class SqlBuilder extends Component
 	 */
 	public function exists(): string
 	{
-		return join(' ', [$this->makeSelect(['0']), $this->make()]);
+		return $this->makeSelect(['0']) . ' ' . $this->make();
 	}
 
 
@@ -286,11 +277,7 @@ class SqlBuilder extends Component
 	 */
 	private function make(): string
 	{
-		return join(' ', [
-			$this->makeCondition(),
-			$this->makeGroup(),
-			$this->makeOrder(),
-		]);
+		return $this->makeCondition() . ' ' . $this->makeGroup() . ' ' . $this->makeOrder();
 	}
 
 	/**
@@ -302,7 +289,7 @@ class SqlBuilder extends Component
 		if (!is_array($select)) {
 			$select = ['*'];
 		}
-		$sql = "SELECT " . implode(',', $select) . " FROM " . $this->getFromAlias();
+		$sql = 'SELECT ' . implode(',', $select) . ' FROM ' . $this->getFromAlias();
 		if ($this->query->join !== []) {
 			$sql .= ' ' . implode(' ', $this->query->join);
 		}
@@ -356,9 +343,9 @@ class SqlBuilder extends Component
 		if ($this->query->offset >= 0 && $this->query->limit >= 1) {
 			$driver = $this->getDriver();
 			if (in_array($driver, ['pgsql', 'postgresql'])) {
-				return ' LIMIT ' . $this->query->limit . ' OFFSET ' . $this->query->offset;
+				return 'LIMIT ' . $this->query->limit . ' OFFSET ' . $this->query->offset;
 			}
-			return ' LIMIT ' . $this->query->offset . ',' . $this->query->limit;
+			return 'LIMIT ' . $this->query->offset . ',' . $this->query->limit;
 		}
 		return '';
 	}