[CALCITE-6624] SqlBabelParser should parse MySQL DATETIME type

babel/src/main/codegen/config.fmpp

@@ -176,6 +176,7 @@ data: {
       "CYCLE"
       "DATA"
 #     "DATE"
+      "DATETIME"
       "DATETIME_DIFF"
       "DAY"
       "DEALLOCATE"

babel/src/test/java/org/apache/calcite/test/BabelQuidemTest.java

@@ -124,6 +124,20 @@ public static void main(String[] args) throws Exception {
                       typeFactory.createSqlType(
                           SqlTypeName.TIMESTAMP_WITH_LOCAL_TIME_ZONE)))
               .connect();
+        case "scott-mysql":
+          return CalciteAssert.that()
+              .with(CalciteAssert.SchemaSpec.SCOTT)
+              .with(CalciteConnectionProperty.FUN, "standard,mysql")
+              .with(CalciteConnectionProperty.LEX, Lex.MYSQL)
+              .with(CalciteConnectionProperty.PARSER_FACTORY,
+                  BabelDdlExecutor.class.getName() + "#PARSER_FACTORY")
+              .with(CalciteConnectionProperty.CONFORMANCE,
+                  SqlConformanceEnum.BABEL)
+              .with(CalciteConnectionProperty.LENIENT_OPERATOR_LOOKUP, true)
+              .with(
+                  ConnectionFactories.addType("DATETIME", typeFactory ->
+                      typeFactory.createSqlType(SqlTypeName.TIMESTAMP)))
+              .connect();
         case "scott-postgresql":
           return CalciteAssert.that()
               .with(CalciteAssert.SchemaSpec.SCOTT)

babel/src/test/resources/sql/mysql.iq

@@ -0,0 +1,39 @@
+# mysql.iq - Babel test for MySQL dialect of SQL
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to you 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.
+#
+!use scott-mysql
+!set outputformat mysql
+
+SELECT cast(cast(TIMESTAMP'1000-01-01 00:00:00' as DATETIME) as DATETIME);
++---------------------+
+| EXPR$0              |
++---------------------+
+| 1000-01-01 00:00:00 |
++---------------------+
+(1 row)
+
+!ok
+
+SELECT cast(cast(TIMESTAMP'9999-12-31 23:59:59' as DATETIME) as DATETIME);
++---------------------+
+| EXPR$0              |
++---------------------+
+| 9999-12-31 23:59:59 |
++---------------------+
+(1 row)
+
+!ok

core/src/main/codegen/templates/Parser.jj

@@ -6154,7 +6154,7 @@ SqlTypeNameSpec CharacterTypeName(Span s) :
 }
 
 /**
-* Parse datetime types: date, time, timestamp.
+* Parse datetime types: date, time, timestamp, datetime.
 */
 SqlTypeNameSpec DateTimeTypeName() :
 {