Treat identity as an auto_increment alias in MSSQLServer mode

Add support for `create table test(id int primary key identity)` statements,
which are common in the SQLServer world.

h2/src/main/org/h2/command/Parser.java

@@ -7491,6 +7491,14 @@ public class Parser {
                 if (readIf("AUTO_INCREMENT")) {
                     parseAutoIncrement(column);
                 }
+                if (database.getMode().useIdentityAsAutoIncrement) {
+                    if (readIf("NOT")) {
+                        read("NULL");
+                    }
+                    if (readIf("IDENTITY")) {
+                        parseAutoIncrement(column);
+                    }
+                }
                 if (affinity) {
                     CreateIndex idx = createAffinityIndex(schema, tableName, cols);
                     command.addConstraintCommand(idx);

h2/src/main/org/h2/engine/Mode.java

@@ -192,6 +192,11 @@ public class Mode {
      */
     public boolean discardWithTableHints;
 
+    /**
+     * Use "IDENTITY" as an alias for "auto_increment" (SQLServer style)
+     */
+    public boolean useIdentityAsAutoIncrement;
+
     /**
      * Convert (VAR)CHAR to VAR(BINARY) and vice versa with UTF-8 encoding instead of HEX.
      */
@@ -262,6 +267,7 @@ public class Mode {
         mode.swapConvertFunctionParameters = true;
         mode.supportPoundSymbolForColumnNames = true;
         mode.discardWithTableHints = true;
+        mode.useIdentityAsAutoIncrement = true;
         // MS SQL Server does not support client info properties. See
         // https://msdn.microsoft.com/en-Us/library/dd571296%28v=sql.110%29.aspx
         mode.supportedClientInfoPropertiesRegEx = null;

h2/src/test/org/h2/test/db/TestCompatibilitySQLServer.java

@@ -4,6 +4,7 @@ import org.h2.test.TestBase;
 import org.h2.test.TestDb;
 
 import java.sql.Connection;
+import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Statement;
 
@@ -25,6 +26,7 @@ public class TestCompatibilitySQLServer extends TestDb {
     @Override
     public void test() throws Exception {
         testDiscardTableHints();
+        testUseIdentityAsAutoIncrementAlias();
     }
 
     private void testDiscardTableHints() throws SQLException {
@@ -35,7 +37,7 @@ public class TestCompatibilitySQLServer extends TestDb {
 
         stat.execute("create table parent(id int primary key, name varchar(255))");
         stat.execute("create table child(id int primary key, parent_id int, name varchar(255), foreign key (parent_id) references public.parent(id))");
-        
+
         assertSupportedSyntax(stat, "select * from parent");
         assertSupportedSyntax(stat, "select * from parent with(nolock)");
         assertSupportedSyntax(stat, "select * from parent with(nolock, index = id)");
@@ -47,6 +49,23 @@ public class TestCompatibilitySQLServer extends TestDb {
         assertSupportedSyntax(stat, "select * from parent p with(nolock) join child ch with(nolock, index(id, name)) on ch.parent_id = p.id");
     }
 
+    private void testUseIdentityAsAutoIncrementAlias() throws SQLException {
+        deleteDb("sqlserver");
+
+        Connection conn = getConnection("sqlserver;MODE=MSSQLServer");
+        Statement stat = conn.createStatement();
+
+        stat.execute("create table test(id int primary key identity, expected_id int)");
+        stat.execute("insert into test (expected_id) VALUES (1), (2), (3)");
+
+        final ResultSet results = stat.executeQuery("select * from test");
+        while (results.next()) {
+            assertEquals(results.getInt("expected_id"), results.getInt("id"));
+        }
+
+        assertSupportedSyntax(stat, "create table test2 (id int primary key not null identity)");
+    }
+
     private void assertSupportedSyntax(Statement stat, String sql) {
         try {
             stat.execute(sql);