try to make var_xxx() and sdtev_xxx() more portable

documentation/src/test/java/org/hibernate/userguide/hql/HQLTest.java

@@ -1795,7 +1795,7 @@ public class HQLTest extends BaseEntityManagerFunctionalTestCase {
 	}
 
 	@Test
-	@RequiresDialect({MySQLDialect.class, PostgreSQLDialect.class, H2Dialect.class, DerbyDialect.class, OracleDialect.class})
+//	@RequiresDialect({MySQLDialect.class, PostgreSQLDialect.class, H2Dialect.class, DerbyDialect.class, OracleDialect.class})
 	public void test_var_function_example() {
 		doInJPA(this::entityManagerFactory, entityManager -> {
 			//tag::hql-native-function-example[]

hibernate-community-dialects/src/main/java/org/hibernate/community/dialect/DB2LegacyDialect.java

@@ -277,9 +277,10 @@ public class DB2LegacyDialect extends Dialect {
 		functionFactory.median();
 		functionFactory.stddev();
 		functionFactory.stddevPopSamp();
+		functionFactory.varPopSamp();
 		functionFactory.regrLinearRegressionAggregates();
 		functionFactory.variance();
-		functionFactory.stdevVarianceSamp();
+		functionFactory.varianceSamp();
 		functionFactory.addYearsMonthsDaysHoursMinutesSeconds();
 		functionFactory.yearsMonthsDaysHoursMinutesSecondsBetween();
 		functionFactory.dateTrunc();

hibernate-core/src/main/java/org/hibernate/dialect/DB2Dialect.java

@@ -259,9 +259,10 @@ public class DB2Dialect extends Dialect {
 		functionFactory.median();
 		functionFactory.stddev();
 		functionFactory.stddevPopSamp();
+		functionFactory.varPopSamp();
 		functionFactory.regrLinearRegressionAggregates();
 		functionFactory.variance();
-		functionFactory.stdevVarianceSamp();
+		functionFactory.varianceSamp();
 		functionFactory.addYearsMonthsDaysHoursMinutesSeconds();
 		functionFactory.yearsMonthsDaysHoursMinutesSecondsBetween();
 		functionFactory.dateTrunc();

hibernate-core/src/main/java/org/hibernate/dialect/SybaseDialect.java

@@ -208,6 +208,13 @@ public class SybaseDialect extends AbstractTransactSQLDialect {
 
 		CommonFunctionFactory functionFactory = new CommonFunctionFactory(queryEngine);
 
+		functionFactory.stddev();
+		functionFactory.variance();
+		functionFactory.stddevPopSamp_stdevp();
+		functionFactory.varPopSamp_varp();
+		functionFactory.stddevPopSamp();
+		functionFactory.varPopSamp();
+
 		// For SQL-Server we need to cast certain arguments to varchar(16384) to be able to concat them
 		queryEngine.getSqmFunctionRegistry().register(
 				"count",

hibernate-core/src/main/java/org/hibernate/dialect/function/CommonFunctionFactory.java

@@ -419,12 +419,7 @@ public class CommonFunctionFactory {
 	/**
 	 * DB2
 	 */
-	public void stdevVarianceSamp() {
+	public void varianceSamp() {
-		functionRegistry.namedAggregateDescriptorBuilder( "stddev_samp" )
-				.setInvariantType(doubleType)
-				.setExactArgumentCount( 1 )
-				.setParameterTypes(NUMERIC)
-				.register();
 		functionRegistry.namedAggregateDescriptorBuilder( "variance_samp" )
 				.setInvariantType(doubleType)
 				.setExactArgumentCount( 1 )

hibernate-core/src/test/java/org/hibernate/orm/test/query/hql/FunctionTests.java

@@ -926,6 +926,16 @@ public class FunctionTests {
 		);
 	}
 
+	@Test
+	public void testStatisticalFunctions(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					session.createQuery("select var_samp(e.theDouble), var_pop(abs(e.theDouble)), stddev_samp(e.theDouble), stddev_pop(e.theDouble) from EntityOfBasics e")
+							.list();
+				}
+		);
+	}
+
 	@Test
 	public void testCurrentDateTimeFunctions(SessionFactoryScope scope) {
 		scope.inTransaction(