diff --git a/jOOQ-test/src/test/java/org/jooq/test/BaseTest.java b/jOOQ-test/src/test/java/org/jooq/test/BaseTest.java
index 934ec71332..bc8bfc3ece 100644
--- a/jOOQ-test/src/test/java/org/jooq/test/BaseTest.java
+++ b/jOOQ-test/src/test/java/org/jooq/test/BaseTest.java
@@ -897,7 +897,11 @@ public abstract class BaseTest<
 
     @SuppressWarnings("unchecked")
     protected Sequence<? extends Number> SAuthorID() throws IllegalAccessException, NoSuchFieldException {
-        return (Sequence<? extends Number>) cSequences().getField("S_AUTHOR_ID").get(cSequences());
+        Class<?> sequences = cSequences();
+
+        return sequences == null
+            ? null
+            : (Sequence<? extends Number>) sequences.getField("S_AUTHOR_ID").get(sequences);
     }
 
     protected final Schema schema() {
diff --git a/jOOQ-test/src/test/java/org/jooq/test/all/testcases/DDLTests.java b/jOOQ-test/src/test/java/org/jooq/test/all/testcases/DDLTests.java
index ebdf043e45..7ba788580d 100644
--- a/jOOQ-test/src/test/java/org/jooq/test/all/testcases/DDLTests.java
+++ b/jOOQ-test/src/test/java/org/jooq/test/all/testcases/DDLTests.java
@@ -135,27 +135,27 @@ extends BaseTest<A, AP, B, S, B2S, BS, L, X, DATE, BOOL, D, T, U, UU, I, IPK, T7
     public void testAlterTableAdd() throws Exception {
         try {
             // TODO: Re-use jOOQ API for this
-            create().execute("create table t (a int)");
+            create().execute("create table t (a " + varchar() + ")");
             create().insertInto(table("t"), field("a")).values(1).execute();
-            assertEquals(asList(1), asList(create().fetchOne(table("t")).intoArray()));
+            assertEquals(asList("1"), asList(create().fetchOne(table("t")).intoArray()));
 
             create().alterTable("t").add("b", SQLDataType.INTEGER).execute();
-            assertEquals(asList(1, null), asList(create().fetchOne(table("t")).intoArray()));
+            assertEquals(asList("1", null), asList(create().fetchOne(table("t")).intoArray()));
 
             create().alterTable("t").add("c", SQLDataType.NUMERIC).execute();
-            assertEquals(asList(1, null, null), asList(create().fetchOne(table("t")).intoArray()));
+            assertEquals(asList("1", null, null), asList(create().fetchOne(table("t")).intoArray()));
 
             create().alterTable("t").add("d", SQLDataType.NUMERIC.precision(5)).execute();
-            assertEquals(asList(1, null, null, null), asList(create().fetchOne(table("t")).intoArray()));
+            assertEquals(asList("1", null, null, null), asList(create().fetchOne(table("t")).intoArray()));
 
             create().alterTable("t").add("e", SQLDataType.NUMERIC.precision(5, 2)).execute();
-            assertEquals(asList(1, null, null, null, null), asList(create().fetchOne(table("t")).intoArray()));
+            assertEquals(asList("1", null, null, null, null), asList(create().fetchOne(table("t")).intoArray()));
 
             create().alterTable("t").add("f", SQLDataType.VARCHAR).execute();
-            assertEquals(asList(1, null, null, null, null, null), asList(create().fetchOne(table("t")).intoArray()));
+            assertEquals(asList("1", null, null, null, null, null), asList(create().fetchOne(table("t")).intoArray()));
 
             create().alterTable("t").add("g", SQLDataType.VARCHAR.length(5)).execute();
-            assertEquals(asList(1, null, null, null, null, null, null), asList(create().fetchOne(table("t")).intoArray()));
+            assertEquals(asList("1", null, null, null, null, null, null), asList(create().fetchOne(table("t")).intoArray()));
         }
         finally {
             create().dropTable("t").execute();
@@ -163,12 +163,13 @@ extends BaseTest<A, AP, B, S, B2S, BS, L, X, DATE, BOOL, D, T, U, UU, I, IPK, T7
     }
 
     public void testAlterTableAlterType() throws Exception {
+        assumeFamilyNotIn(FIREBIRD);
+
         try {
             // TODO: Re-use jOOQ API for this
             create().execute("create table t (a int)");
-            create().insertInto(table("t"), field("a")).values(1).execute();
-
             create().alterTable("t").alter("a").set(SQLDataType.VARCHAR).execute();
+            create().insertInto(table("t"), field("a")).values("1").execute();
             assertEquals("1", create().fetchOne("select * from t").getValue(0));
         }
         finally {
@@ -179,7 +180,7 @@ extends BaseTest<A, AP, B, S, B2S, BS, L, X, DATE, BOOL, D, T, U, UU, I, IPK, T7
     public void testAlterTableAlterDefault() throws Exception {
         try {
             // TODO: Re-use jOOQ API for this
-            create().execute("create table t (a int, b " + SQLDataType.VARCHAR.length(10).getCastTypeName(create().configuration()) + ")");
+            create().execute("create table t (a int, b " + varchar() + ")");
 
             create().alterTable("t").alter("b").defaultValue("empty").execute();
             create().insertInto(table("t"), field("a")).values(1).execute();
@@ -193,15 +194,15 @@ extends BaseTest<A, AP, B, S, B2S, BS, L, X, DATE, BOOL, D, T, U, UU, I, IPK, T7
     public void testAlterTableDrop() throws Exception {
         try {
             // TODO: Re-use jOOQ API for this
-            create().execute("create table t (a int, b int, c int)");
-            create().insertInto(table("t"), field("a"), field("b"), field("c")).values(1, 2, 3).execute();
-            assertEquals(asList(1, 2, 3), asList(create().fetchOne(table("t")).intoArray()));
+            create().execute("create table t (a " + varchar() + ", b " + varchar() + ", c " + varchar() + ")");
+            create().insertInto(table("t"), field("a"), field("b"), field("c")).values("1", "2", "3").execute();
+            assertEquals(asList("1", "2", "3"), asList(create().fetchOne(table("t")).intoArray()));
 
             create().alterTable("t").drop("c").execute();
-            assertEquals(asList(1, 2), asList(create().fetchOne(table("t")).intoArray()));
+            assertEquals(asList("1", "2"), asList(create().fetchOne(table("t")).intoArray()));
 
             create().alterTable("t").drop("b").execute();
-            assertEquals(asList(1), asList(create().fetchOne(table("t")).intoArray()));
+            assertEquals(asList("1"), asList(create().fetchOne(table("t")).intoArray()));
         }
         finally {
             create().dropTable("t").execute();
@@ -211,9 +212,9 @@ extends BaseTest<A, AP, B, S, B2S, BS, L, X, DATE, BOOL, D, T, U, UU, I, IPK, T7
     public void testDropTable() throws Exception {
 
         // TODO: Re-use jOOQ API for this
-        create().execute("create table t (a int, b int, c int)");
-        create().insertInto(table("t"), field("a"), field("b"), field("c")).values(1, 2, 3).execute();
-        assertEquals(asList(1, 2, 3), asList(create().fetchOne(table("t")).intoArray()));
+        create().execute("create table t (a " + varchar() + ", b " + varchar() + ", c " + varchar() + ")");
+        create().insertInto(table("t"), field("a"), field("b"), field("c")).values("1", "2", "3").execute();
+        assertEquals(asList("1", "2", "3"), asList(create().fetchOne(table("t")).intoArray()));
 
         create().dropTable("t").execute();
         try {
@@ -222,4 +223,8 @@ extends BaseTest<A, AP, B, S, B2S, BS, L, X, DATE, BOOL, D, T, U, UU, I, IPK, T7
         }
         catch (DataAccessException expected) {}
     }
+
+    private String varchar() {
+        return SQLDataType.VARCHAR.length(10).getCastTypeName(create().configuration());
+    }
 }
diff --git a/jOOQ-test/src/test/java/org/jooq/test/all/testcases/GeneralTests.java b/jOOQ-test/src/test/java/org/jooq/test/all/testcases/GeneralTests.java
index a4f42a1a3e..be4b65b8ec 100644
--- a/jOOQ-test/src/test/java/org/jooq/test/all/testcases/GeneralTests.java
+++ b/jOOQ-test/src/test/java/org/jooq/test/all/testcases/GeneralTests.java
@@ -57,6 +57,7 @@ import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.fail;
+import static org.junit.Assume.assumeNotNull;
 
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
@@ -128,15 +129,15 @@ extends BaseTest<A, AP, B, S, B2S, BS, L, X, DATE, BOOL, D, T, U, UU, I, IPK, T7
     }
 
     public void testSequences() throws Exception {
+        assumeNotNull(SAuthorID());
+
         testSequences0(SAuthorID());
     }
 
     public void testSequenceByName() throws Exception {
-        Sequence<? extends Number> sequence = SAuthorID();
+        assumeNotNull(SAuthorID());
 
-        if (sequence != null) {
-            testSequences0(DSL.sequenceByName(sequence.getSchema().getName(), sequence.getName()));
-        }
+        testSequences0(DSL.sequenceByName(SAuthorID().getSchema().getName(), SAuthorID().getName()));
     }
 
     private void testSequences0(Sequence<? extends Number> sequence) {
diff --git a/jOOQ-test/src/test/java/org/jooq/test/all/testcases/PredicateTests.java b/jOOQ-test/src/test/java/org/jooq/test/all/testcases/PredicateTests.java
index ae4836fc73..7ec34f1512 100644
--- a/jOOQ-test/src/test/java/org/jooq/test/all/testcases/PredicateTests.java
+++ b/jOOQ-test/src/test/java/org/jooq/test/all/testcases/PredicateTests.java
@@ -46,6 +46,8 @@ import static java.util.Arrays.asList;
 // ...
 import static org.jooq.SQLDialect.DERBY;
 // ...
+import static org.jooq.SQLDialect.MARIADB;
+import static org.jooq.SQLDialect.MYSQL;
 import static org.jooq.conf.StatementType.STATIC_STATEMENT;
 import static org.jooq.impl.DSL.all;
 import static org.jooq.impl.DSL.any;
@@ -527,6 +529,10 @@ extends BaseTest<A, AP, B, S, B2S, BS, L, X, DATE, BOOL, D, T, U, UU, I, IPK, T7
     }
 
     public void testInPredicateWithSubselectAndLimitOffset() throws Exception {
+
+        // This query is not yet supported in these databases
+        assumeFamilyNotIn(MARIADB, MYSQL);
+
         Result<Record1<Integer>> result =
         create().select(TBook_ID())
                 .from(TBook())
diff --git a/jOOQ/src/main/java/org/jooq/AlterTableAlterStep.java b/jOOQ/src/main/java/org/jooq/AlterTableAlterStep.java
index f650c798c1..1fc41b78a2 100644
--- a/jOOQ/src/main/java/org/jooq/AlterTableAlterStep.java
+++ b/jOOQ/src/main/java/org/jooq/AlterTableAlterStep.java
@@ -40,6 +40,22 @@
  */
 package org.jooq;
 
+// ...
+// ...
+import static org.jooq.SQLDialect.CUBRID;
+// ...
+import static org.jooq.SQLDialect.DERBY;
+import static org.jooq.SQLDialect.H2;
+import static org.jooq.SQLDialect.HSQLDB;
+// ...
+import static org.jooq.SQLDialect.MARIADB;
+import static org.jooq.SQLDialect.MYSQL;
+// ...
+import static org.jooq.SQLDialect.POSTGRES;
+import static org.jooq.SQLDialect.SQLITE;
+// ...
+// ...
+
 import org.jooq.api.annotation.State;
 
 /**
@@ -54,15 +70,18 @@ public interface AlterTableAlterStep<T> {
     /**
      * Specify a new column <code>DEFAULT</code>.
      */
+    @Support
     AlterTableFinalStep defaultValue(T literal);
 
     /**
      * Specify a new column <code>DEFAULT</code>.
      */
+    @Support
     AlterTableFinalStep defaultValue(Field<T> expression);
 
     /**
      * Specify a new column data type.
      */
+    @Support({ CUBRID, DERBY, H2, HSQLDB, MARIADB, MYSQL, POSTGRES, SQLITE })
     AlterTableFinalStep set(DataType<?> type);
 }
diff --git a/jOOQ/src/main/java/org/jooq/AlterTableDropStep.java b/jOOQ/src/main/java/org/jooq/AlterTableDropStep.java
index baafeebf5e..4827d03da7 100644
--- a/jOOQ/src/main/java/org/jooq/AlterTableDropStep.java
+++ b/jOOQ/src/main/java/org/jooq/AlterTableDropStep.java
@@ -55,11 +55,13 @@ public interface AlterTableDropStep extends AlterTableFinalStep {
      * Add a <code>CASCADE</code> clause to the
      * <code>ALTER TABLE .. DROP COLUMN</code> statement.
      */
+    @Support
     AlterTableFinalStep cascade();
 
     /**
      * Add a <code>RESTRICT</code> clause to the
      * <code>ALTER TABLE .. DROP COLUMN</code> statement.
      */
+    @Support
     AlterTableFinalStep restrict();
 }
diff --git a/jOOQ/src/main/java/org/jooq/AlterTableStep.java b/jOOQ/src/main/java/org/jooq/AlterTableStep.java
index 19b4e2373b..dbfb869c59 100644
--- a/jOOQ/src/main/java/org/jooq/AlterTableStep.java
+++ b/jOOQ/src/main/java/org/jooq/AlterTableStep.java
@@ -54,35 +54,41 @@ public interface AlterTableStep {
      * Add an <code>ALTER COLUMN</code> clause to the <code>ALTER TABLE</code>
      * statement.
      */
+    @Support
     <T> AlterTableAlterStep<T> alter(Field<T> field);
 
     /**
      * Add an <code>ALTER COLUMN</code> clause to the <code>ALTER TABLE</code>
      * statement.
      */
+    @Support
     AlterTableAlterStep<Object> alter(String field);
 
     /**
      * Add an <code>ADD COLUMN</code> clause to the <code>ALTER TABLE</code>
      * statement.
      */
+    @Support
     <T> AlterTableFinalStep add(Field<T> field, DataType<T> type);
 
     /**
      * Add an <code>ADD COLUMN</code> clause to the <code>ALTER TABLE</code>
      * statement.
      */
+    @Support
     AlterTableFinalStep add(String field, DataType<?> type);
 
     /**
      * Add an <code>DROP COLUMN</code> clause to the <code>ALTER TABLE</code>
      * statement.
      */
+    @Support
     AlterTableDropStep drop(Field<?> field);
 
     /**
      * Add an <code>DROP COLUMN</code> clause to the <code>ALTER TABLE</code>
      * statement.
      */
+    @Support
     AlterTableDropStep drop(String field);
 }
diff --git a/jOOQ/src/main/java/org/jooq/DropTableStep.java b/jOOQ/src/main/java/org/jooq/DropTableStep.java
index 839aaf0021..411254f172 100644
--- a/jOOQ/src/main/java/org/jooq/DropTableStep.java
+++ b/jOOQ/src/main/java/org/jooq/DropTableStep.java
@@ -55,11 +55,13 @@ public interface DropTableStep extends DropTableFinalStep {
      * Add a <code>CASCADE</code> clause to the <code>DROP TABLE</code>
      * statement.
      */
+    @Support
     DropTableFinalStep cascade();
 
     /**
      * Add a <code>RESTRICT</code> clause to the <code>DROP TABLE</code>
      * statement.
      */
+    @Support
     DropTableFinalStep restrict();
 }
diff --git a/jOOQ/src/main/java/org/jooq/impl/AlterTableImpl.java b/jOOQ/src/main/java/org/jooq/impl/AlterTableImpl.java
index f2ea6ade62..9a051c4341 100644
--- a/jOOQ/src/main/java/org/jooq/impl/AlterTableImpl.java
+++ b/jOOQ/src/main/java/org/jooq/impl/AlterTableImpl.java
@@ -40,15 +40,12 @@
  */
 package org.jooq.impl;
 
-import static java.util.Arrays.asList;
 import static org.jooq.Clause.ALTER_TABLE;
 import static org.jooq.Clause.ALTER_TABLE_ADD;
 import static org.jooq.Clause.ALTER_TABLE_ALTER;
 import static org.jooq.Clause.ALTER_TABLE_ALTER_DEFAULT;
 import static org.jooq.Clause.ALTER_TABLE_DROP;
 import static org.jooq.Clause.ALTER_TABLE_TABLE;
-// ...
-import static org.jooq.SQLDialect.POSTGRES;
 import static org.jooq.impl.DSL.field;
 import static org.jooq.impl.DSL.inline;
 
@@ -190,21 +187,37 @@ class AlterTableImpl extends AbstractQuery implements
             ctx.end(ALTER_TABLE_ADD);
         }
         else if (alter != null) {
-            ctx.start(ALTER_TABLE_ALTER)
-               .sql(" ").keyword("alter").sql(" ")
+            ctx.start(ALTER_TABLE_ALTER);
+
+            switch (family) {
+                /* [pro] xx
+                xxxx xxxxxxx
+                    xxxxxxxxx xxxxxxxxxxxxxxxxxxxxx
+                    xxxxxx
+                xx [/pro] */
+
+                default:
+                    ctx.sql(" ").keyword("alter");
+                    break;
+            }
+
+            ctx.sql(" ")
                .qualify(false)
                .visit(alter)
                .qualify(true);
 
             if (alterType != null) {
-                if (asList(POSTGRES).contains(family)) {
-                    ctx.sql(" ").keyword("type");
+                switch (family) {
+                    /* [pro] xx
+                    xxxx xxxx
+                        xxxxxxxxx xxxxxxxxxxxxxxx xxxx xxxxxxx
+                        xxxxxx
+                    xx [/pro] */
+
+                    case POSTGRES:
+                        ctx.sql(" ").keyword("type");
+                        break;
                 }
-                /* [pro] xx
-                xxxx xx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx x
-                    xxxxxxxxx xxxxxxxxxxxxxxx xxxx xxxxxxx
-                x
-                xx [/pro] */
 
                 ctx.sql(" ").keyword(alterType.getCastTypeName(ctx.configuration()));
 
@@ -213,16 +226,42 @@ class AlterTableImpl extends AbstractQuery implements
                 }
             }
             else if (alterDefault != null) {
-                ctx.start(ALTER_TABLE_ALTER_DEFAULT)
-                   .sql(" ").keyword("set default").sql(" ").visit(alterDefault)
+                ctx.start(ALTER_TABLE_ALTER_DEFAULT);
+
+                switch (family) {
+                    /* [pro] xx
+                    xxxx xxxxxxx
+                        xxxxxxxxx xxxxxxxxxxxxxxxxxxxxxx
+                        xxxxxx
+                    xx [/pro] */
+
+                    default:
+                        ctx.sql(" ").keyword("set default");
+                        break;
+                }
+
+                ctx.sql(" ").visit(alterDefault)
                    .end(ALTER_TABLE_ALTER_DEFAULT);
             }
 
             ctx.end(ALTER_TABLE_ALTER);
         }
         else if (drop != null) {
-            ctx.start(ALTER_TABLE_DROP)
-               .sql(" ").keyword("drop").sql(" ")
+            ctx.start(ALTER_TABLE_DROP);
+
+            switch (family) {
+                /* [pro] xx
+                xxxx xxxxxxx
+                    xxxxxxxxx xxxxxxxxxxxxxxxx xxxxxxxxx
+                    xxxxxx
+                xx [/pro] */
+
+                default:
+                    ctx.sql(" ").keyword("drop");
+                    break;
+            }
+
+            ctx.sql(" ")
                .qualify(false)
                .visit(drop)
                .qualify(true);