progress

src/main/java/typewriter/maria/MariaDB.java

@@ -100,11 +100,11 @@ public void createDatabase(String url) {
      * {@inheritDoc}
      */
     @Override
-    public void commandLimitAndOffset(SQL builder, long limit, long offset) {
-        if (0 < limit) builder.write("LIMIT").write(limit);
+    public void commandLimitAndOffset(SQL sql, long limit, long offset) {
+        sql.limit(limit);
         if (0 < offset) {
-            if (limit <= 0) builder.write("LIMIT 18446744073709551615");
-            builder.write(" OFFSET ").write(offset);
+            if (limit <= 0) sql.limit(Long.MAX_VALUE);
+            sql.offset(offset);
         }
     }
 

src/main/java/typewriter/query/Query.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2023 Nameless Production Committee
+ *
+ * Licensed under the MIT License (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *          http://opensource.org/licenses/mit-license.php
+ */
+package typewriter.query;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import typewriter.api.Identifiable;
+import typewriter.api.Specifier;
+
+public abstract class Query<M extends Identifiable> {
+
+    private final List<String> select = new ArrayList();
+
+    /**
+     * Declare SELECT statement.
+     * 
+     * @param names
+     */
+    protected final void SELECT(Specifier<M, ?>... names) {
+        SELECT(Stream.of(names).map(Specifier::propertyName).toList());
+    }
+
+    /**
+     * Declare SELECT statement.
+     * 
+     * @param names
+     */
+    protected final void SELECT(String... names) {
+        SELECT(List.of(names));
+    }
+
+    /**
+     * Declare SELECT statement.
+     * 
+     * @param names
+     */
+    protected final void SELECT(List<String> names) {
+        select.addAll(names);
+    }
+
+    /**
+     * Test query.
+     * 
+     * @param query
+     * @return
+     */
+    public boolean is(String query) {
+        return query.equals(toString());
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public String toString() {
+        StringBuilder builder = new StringBuilder();
+
+        // SELECT
+        builder.append("SELECT ").append(select.stream().collect(Collectors.joining(", ")));
+
+        return builder.toString();
+    }
+}

src/main/java/typewriter/rdb/Dialect.java

@@ -149,8 +149,7 @@ public String commandUpdate() {
      * @param offset
      */
     public void commandLimitAndOffset(SQL sql, long limit, long offset) {
-        if (0 < limit) sql.write("LIMIT").write(limit);
-        if (0 < offset) sql.write("OFFSET").write(offset);
+        sql.limit(limit).offset(offset);
     }
 
     /**

src/main/java/typewriter/rdb/RDB.java

@@ -142,7 +142,7 @@ protected RDBQuery<M> createQueryable() {
      */
     @Override
     public long count() {
-        return new SQL<>(this).write("SELECT count(*) N").from(tableName).qurey().map(result -> result.getLong("N")).to().exact();
+        return new SQL<>(this).select("count(*)").from(tableName).qurey().map(result -> result.getLong(1)).to().exact();
     }
 
     /**

src/main/java/typewriter/rdb/SQL.java

@@ -300,6 +300,26 @@ public SQL<M> orderBy(Specifier<M, ?> specifier1, boolean ascending1, Specifier<
         return this;
     }
 
+    /**
+     * Write SELECT statement.
+     * 
+     * @return
+     */
+    public SQL<M> distinct(String... specifiers) {
+        text.append(" SELECT DISTINCT ").append(Stream.of(specifiers).collect(Collectors.joining(", ")));
+        return this;
+    }
+
+    /**
+     * Write SELECT statement.
+     * 
+     * @return
+     */
+    public SQL<M> select(String... specifiers) {
+        text.append(" SELECT ").append(Stream.of(specifiers).collect(Collectors.joining(", ")));
+        return this;
+    }
+
     /**
      * Write SELECT statement.
      * 
@@ -321,6 +341,16 @@ public SQL<M> avg(Specifier<M, ?> specifier, int windowSize) {
         return this;
     }
 
+    public SQL<M> limit(long size) {
+        if (0 < size) text.append(" LIMIT ").append(size);
+        return this;
+    }
+
+    public SQL<M> offset(long size) {
+        if (0 < size) text.append(" OFFSET ").append(size);
+        return this;
+    }
+
     /**
      * Write WHERE statement.
      * 

src/test/java/typewriter/query/QueryTest.java

@@ -0,0 +1,104 @@
+/*
+ * Copyright (C) 2023 Nameless Production Committee
+ *
+ * Licensed under the MIT License (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *          http://opensource.org/licenses/mit-license.php
+ */
+package typewriter.query;
+
+import org.junit.jupiter.api.Test;
+
+import typewriter.api.model.IdentifiableModel;
+
+public class QueryTest {
+
+    @Test
+    void selectName() {
+        Query query = new Query() {
+            {
+                SELECT("test");
+            }
+        };
+
+        assert query.is("SELECT test");
+    }
+
+    @Test
+    void selectNames() {
+        Query query = new Query() {
+            {
+                SELECT("first", "second");
+            }
+        };
+
+        assert query.is("SELECT first, second");
+    }
+
+    @Test
+    void selectSpecifier() {
+        Query query = new Query<Person>() {
+            {
+                SELECT(Person::getName);
+            }
+        };
+
+        assert query.is("SELECT name");
+    }
+
+    @Test
+    void selectSpecifiers() {
+        Query query = new Query() {
+            {
+                SELECT("first", "second");
+            }
+        };
+
+        assert query.is("SELECT first, second");
+    }
+
+    /**
+     * 
+     */
+    static class Person extends IdentifiableModel {
+
+        public String name;
+
+        public int age;
+
+        /**
+         * Create empty model.
+         */
+        public Person() {
+        }
+
+        /**
+         * @param name
+         * @param age
+         */
+        public Person(String name, int age) {
+            this.name = name;
+            this.age = age;
+        }
+
+        /**
+         * Get the name property of this {@link Person}.
+         * 
+         * @return The name property.
+         */
+        public String getName() {
+            return name;
+        }
+
+        /**
+         * Get the age property of this {@link Person}.
+         * 
+         * @return The age property.
+         */
+        public int getAge() {
+            return age;
+        }
+    }
+}