added possibility to query correlated outer tables in select statements

Author: clausnagel

src/main/java/org/citydb/sqlbuilder/select/Select.java

@@ -378,6 +378,29 @@ public Set<Table> getInvolvedTables() {
         return tables;
     }
 
+    public Set<Table> getOuterTables() {
+        Set<Table> tables = new LinkedHashSet<>();
+
+        for (PredicateToken token : predicateTokens)
+            token.getInvolvedTables(tables);
+
+        for (HavingToken token : havingTokens)
+            token.getInvolvedTables(tables);
+
+        for (OrderByToken token : orderByTokens)
+            token.getInvolvedTables(tables);
+
+        if (offsetToken != null)
+            offsetToken.getInvolvedTables(tables);
+
+        if (fetchToken != null)
+            fetchToken.getInvolvedTables(tables);
+
+        tables.removeAll(getInvolvedTables());
+
+        return tables;
+    }
+
     @Override
     public List<PlaceHolder<?>> getInvolvedPlaceHolders() {
         List<PlaceHolder<?>> statements = new ArrayList<>();

src/main/java/org/citydb/sqlbuilder/select/operator/comparison/AbstractComparisonOperator.java

@@ -25,6 +25,7 @@
 import org.citydb.sqlbuilder.schema.Table;
 import org.citydb.sqlbuilder.select.PredicateToken;
 import org.citydb.sqlbuilder.select.ProjectionToken;
+import org.citydb.sqlbuilder.select.Select;
 import org.citydb.sqlbuilder.select.operator.Operator;
 
 import java.util.List;
@@ -37,6 +38,8 @@ public void getInvolvedTables(Expression operand, Set<Table> tables) {
             ((ProjectionToken) operand).getInvolvedTables(tables);
         else if (operand instanceof PredicateToken)
             ((PredicateToken) operand).getInvolvedTables(tables);
+        else if (operand instanceof Select)
+            tables.addAll(((Select) operand).getOuterTables());
     }
 
     public void getInvolvedPlaceHolders(Expression operand, List<PlaceHolder<?>> statements) {

src/main/java/org/citydb/sqlbuilder/select/projection/ColumnExpression.java

@@ -50,7 +50,7 @@ public String getAsName() {
 
     @Override
     public void getInvolvedTables(Set<Table> tables) {
-        // nothing to do here
+        tables.addAll(select.getOuterTables());
     }
 
     @Override