[CALCITE-6624] SqlParser should parse MySQL DATETIME type

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 +1,22 @@
+!use scott-mysql
+!set outputformat mysql
+
+SELECT cast(cast(DATETIME '1000-01-01 00:00:00' as DATETIME) as DATETIME);
++---------------------+
+| EXPR$0              |
++---------------------+
+| 1000-01-01 00:00:00 |
++---------------------+
+(1 row)
+
+!ok
+
+SELECT cast(cast(DATETIME '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() :
 {
@@ -6182,6 +6182,12 @@ SqlTypeNameSpec DateTimeTypeName() :
     {
         return new SqlBasicTypeNameSpec(typeName, precision, s.end(this));
     }
+|
+    <DATETIME> { s = span(); }
+    precision = PrecisionOpt()
+    {
+        return new SqlBasicTypeNameSpec(SqlTypeName.TIMESTAMP, precision, s.end(this));
+    }
 }
 
 // Parse an optional data type precision, default is -1.