Added support for unions as subselect

- fixed old bug where subselect's values were lost

Author: sgflt

src/main/java/eu/qwsome/sql/Select.java

@@ -23,6 +23,10 @@ public class Select implements Query {
    * A list of joins that generates multiple JOIN clauses.
    */
   private final List<Join> joins = new ArrayList<>();
+  /**
+   * A list of conditions from subselects
+   */
+  private final List<Condition> subselectConditions = new ArrayList<>();
   /**
    * True if SELECT DISTINCT shall be used
    */
@@ -37,6 +41,10 @@ public class Select implements Query {
   private Condition condition;
   private OrderBy orderBy;
   private GroupBy groupBy;
+  /**
+   * This may contain conditions from unin used as subselect
+   */
+  private final List<ValueBinding> union = new ArrayList<>();
 
 
   /**
@@ -159,6 +167,12 @@ public TableSelectedPhase from(final Query subquery, final String alias) {
         .concat(" ) AS ")
         .concat(alias);
 
+    if (subquery instanceof ConditionsBuiltPhase) {
+      this.subselectConditions.add(((ConditionsBuiltPhase) subquery).getSelect().condition);
+    } else if (subquery instanceof ValueBinding) {
+      this.union.add((ValueBinding) subquery);
+    }
+
     return new TableSelectedPhase();
   }
 
@@ -175,7 +189,8 @@ public String toSql() {
         .append(this.distinct ? "DISTINCT " : "")
         .append(getColumns())
         .append(" FROM ")
-        .append(this.source);
+        .append(this.source)
+    ;
 
     if (!this.joins.isEmpty()) {
       for (final var join : this.joins) {
@@ -221,15 +236,22 @@ private GroupByPhase groupBy(final Column... groupByColumns) {
 
 
   private ValueConstructor toValuesInternal() {
-    if (Select.this.condition == null && Select.this.joins.isEmpty()) {
-      return new ValueConstructor();
-    }
-
     final var values = new ValueConstructor();
 
     Select.this.joins.stream()
         .map(Join::toValues)
-        .forEach(values::add);
+        .forEach(values::add)
+    ;
+
+    Select.this.subselectConditions.stream()
+        .map(Condition::getValues)
+        .forEach(values::add)
+    ;
+
+    Select.this.union.stream()
+        .map(ValueBinding::toValues)
+        .forEach(values::add)
+    ;
 
     if (this.condition != null) {
       values.add(Select.this.condition.getValues());
@@ -366,6 +388,11 @@ public ValueConstructor toValues() {
     }
 
 
+    Select getSelect() {
+      return Select.this;
+    }
+
+
     /**
      * Adds an order by clause to the statement.
      *
@@ -381,6 +408,11 @@ public OrderByPhase orderBy(final Column... columns) {
     public GroupByPhase groupBy(final Column... columns) {
       return Select.this.groupBy(columns);
     }
+
+
+    public Union union(final ConditionsBuiltPhase otherSelect) {
+      return Union.of(this, otherSelect);
+    }
   }
 
   /**

src/main/java/eu/qwsome/sql/Union.java

@@ -1,10 +1,10 @@
 package eu.qwsome.sql;
 
-import eu.qwsome.sql.condition.ValueConstructor;
-
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
+import eu.qwsome.sql.condition.ValueConstructor;
+
 /**
  * @author Lukáš Kvídera
  */
@@ -40,15 +40,15 @@ public static Union allOf(final ValueBinding... queries) {
 
   @Override
   public String toSql() {
-    final String keyword = this.all ? " UNION ALL " : " UNION ";
+    final var keyword = this.all ? " UNION ALL " : " UNION ";
     return Stream.of(this.queries)
       .map(Query::toSql)
       .collect(Collectors.joining(keyword));
   }
 
   @Override
   public ValueConstructor toValues() {
-    final ValueConstructor values = new ValueConstructor();
+    final var values = new ValueConstructor();
     Stream.of(this.queries)
       .map(ValueBinding::toValues)
       .forEach(values::add);