improved sql parser. for issue #2082

src/main/java/com/alibaba/druid/sql/dialect/mysql/parser/MySqlStatementParser.java

@@ -3391,6 +3391,11 @@ public class MySqlStatementParser extends SQLStatementParser {
                     // " " + lexer.stringVal());
                     SQLAlterTableAddIndex item = parseAlterTableAddIndex();
                     item.setParent(stmt);
+                    stmt.addItem(item);
+                } else if (lexer.token() == Token.FOREIGN) {
+                    MysqlForeignKey fk = this.getExprParser().parseForeignKey();
+                    SQLAlterTableAddConstraint item = new SQLAlterTableAddConstraint(fk);
+
                     stmt.addItem(item);
                 } else if (lexer.token() == Token.CONSTRAINT) {
                     lexer.nextToken();

src/test/java/com/alibaba/druid/bvt/sql/mysql/alter/MySqlAlterTableTest30.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 1999-2017 Alibaba Group Holding Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.alibaba.druid.bvt.sql.mysql.alter;
+
+import com.alibaba.druid.sql.SQLUtils;
+import com.alibaba.druid.sql.ast.SQLStatement;
+import com.alibaba.druid.sql.dialect.mysql.parser.MySqlStatementParser;
+import com.alibaba.druid.sql.parser.Token;
+import junit.framework.TestCase;
+import org.junit.Assert;
+
+public class MySqlAlterTableTest30 extends TestCase {
+
+    public void test_alter_add_key() throws Exception {
+        String sql = "ALTER TABLE test_table_normal\n" +
+                "ADD FOREIGN KEY (stuID)\n" +
+                "REFERENCES Persons(stuID);";
+        MySqlStatementParser parser = new MySqlStatementParser(sql);
+        SQLStatement stmt = parser.parseStatementList().get(0);
+        parser.match(Token.EOF);
+        String output = SQLUtils.toMySqlString(stmt);
+        Assert.assertEquals("ALTER TABLE test_table_normal\n" +
+                "\tADD FOREIGN KEY (stuID) REFERENCES Persons (stuID);", output);
+    }
+}