improve sqlparser

src/main/java/com/alibaba/druid/sql/parser/SQLExprParser.java

@@ -319,6 +319,7 @@ public SQLExpr primary() {
             case ESCAPE:
             case OVER:
             case ORDER:
+            case CONSTRAINT:
                 sqlExpr = new SQLIdentifierExpr(lexer.stringVal());
                 lexer.nextToken();
                 break;

src/main/java/com/alibaba/druid/sql/parser/SQLParser.java

@@ -193,6 +193,7 @@ protected String as() {
         switch (lexer.token()) {
             case KEY:
             case INTERVAL:
+            case CONSTRAINT:
                 alias = lexer.token().name();
                 lexer.nextToken();
                 return alias;

src/test/java/com/alibaba/druid/bvt/sql/mysql/MySqlSelectTest_22.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright 1999-2011 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;
+
+import java.util.List;
+
+import org.junit.Assert;
+
+import com.alibaba.druid.sql.MysqlTest;
+import com.alibaba.druid.sql.ast.SQLStatement;
+import com.alibaba.druid.sql.dialect.mysql.parser.MySqlStatementParser;
+import com.alibaba.druid.sql.dialect.mysql.visitor.MySqlSchemaStatVisitor;
+
+public class MySqlSelectTest_22 extends MysqlTest {
+
+    public void test_0() throws Exception {
+        String sql = "select CONSTRAINT constraint from t where id = 1 order by constraint desc";
+
+
+        MySqlStatementParser parser = new MySqlStatementParser(sql);
+        List<SQLStatement> statementList = parser.parseStatementList();
+        SQLStatement statemen = statementList.get(0);
+        print(statementList);
+
+        Assert.assertEquals(1, statementList.size());
+
+        MySqlSchemaStatVisitor visitor = new MySqlSchemaStatVisitor();
+        statemen.accept(visitor);
+
+        System.out.println("Tables : " + visitor.getTables());
+        System.out.println("fields : " + visitor.getColumns());
+        System.out.println("coditions : " + visitor.getConditions());
+        System.out.println("orderBy : " + visitor.getOrderByColumns());
+
+        Assert.assertEquals(1, visitor.getTables().size());
+        Assert.assertEquals(2, visitor.getColumns().size());
+        Assert.assertEquals(1, visitor.getConditions().size());
+        Assert.assertEquals(1, visitor.getOrderByColumns().size());
+    }
+
+
+
+}