Fixes #9790: Fixed yii\db\sqlite\QueryBuilder to generate proper SQL for UNION

framework/db/sqlite/QueryBuilder.php

@@ -356,4 +356,56 @@ class QueryBuilder extends \yii\db\QueryBuilder
 
         return '(' . implode($operator === 'IN' ? ' OR ' : ' AND ', $vss) . ')';
     }
+
+    /**
+     * @inheritdoc
+     */
+    public function build($query, $params = [])
+    {
+        $query = $query->prepare($this);
+
+        $params = empty($params) ? $query->params : array_merge($params, $query->params);
+
+        $clauses = [
+            $this->buildSelect($query->select, $params, $query->distinct, $query->selectOption),
+            $this->buildFrom($query->from, $params),
+            $this->buildJoin($query->join, $params),
+            $this->buildWhere($query->where, $params),
+            $this->buildGroupBy($query->groupBy),
+            $this->buildHaving($query->having, $params),
+        ];
+
+        $sql = implode($this->separator, array_filter($clauses));
+        $sql = $this->buildOrderByAndLimit($sql, $query->orderBy, $query->limit, $query->offset);
+
+        $union = $this->buildUnion($query->union, $params);
+        if ($union !== '') {
+            $sql = "$sql{$this->separator}$union";
+        }
+
+        return [$sql, $params];
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function buildUnion($unions, &$params)
+    {
+        if (empty($unions)) {
+            return '';
+        }
+
+        $result = '';
+
+        foreach ($unions as $i => $union) {
+            $query = $union['query'];
+            if ($query instanceof Query) {
+                list($unions[$i]['query'], $params) = $this->build($query, $params);
+            }
+
+            $result .= ' UNION ' . ($union['all'] ? 'ALL ' : '') . ' ' . $unions[$i]['query'];
+        }
+
+        return trim($result);
+    }
 }