Support DuckDB UNPIVOT statement

Adds the simplified statement form UNPIVOT tbl ON columns
[INTO NAME name VALUE values] as UnPivotQuery, the counterpart of the
existing PivotQuery. The FROM-clause form UNPIVOT (...) is unaffected.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EqinwHBKuAtPEmtXr3b5P2

Author: hayssams

src/main/java/net/sf/jsqlparser/statement/select/FromItemVisitor.java

@@ -92,6 +92,14 @@ default void visit(PivotQuery pivotQuery) {
         this.visit(pivotQuery, null);
     }
 
+    default <S> T visit(UnPivotQuery unPivotQuery, S context) {
+        return null;
+    }
+
+    default void visit(UnPivotQuery unPivotQuery) {
+        this.visit(unPivotQuery, null);
+    }
+
     <S> T visit(SetOperationList setOperationList, S context);
 
     default void visit(SetOperationList setOperationList) {

src/main/java/net/sf/jsqlparser/statement/select/FromItemVisitorAdapter.java

@@ -129,6 +129,11 @@ public <S> T visit(PivotQuery pivotQuery, S context) {
         return pivotQuery.accept(selectVisitor, context);
     }
 
+    @Override
+    public <S> T visit(UnPivotQuery unPivotQuery, S context) {
+        return unPivotQuery.accept(selectVisitor, context);
+    }
+
     @Override
     public <S> T visit(SetOperationList setOperationList, S context) {
         ArrayList<T> results = new ArrayList<>();

src/main/java/net/sf/jsqlparser/statement/select/SelectVisitor.java

@@ -47,6 +47,14 @@ default void visit(PivotQuery pivotQuery) {
         this.visit(pivotQuery, null);
     }
 
+    default <S> T visit(UnPivotQuery unPivotQuery, S context) {
+        return null;
+    }
+
+    default void visit(UnPivotQuery unPivotQuery) {
+        this.visit(unPivotQuery, null);
+    }
+
     <S> T visit(FromQuery fromQuery, S context);
 
     <S> T visit(SetOperationList setOpList, S context);

src/main/java/net/sf/jsqlparser/statement/select/SelectVisitorAdapter.java

@@ -272,6 +272,16 @@ public <S> T visit(PivotQuery pivotQuery, S context) {
         return null;
     }
 
+    @Override
+    public <S> T visit(UnPivotQuery unPivotQuery, S context) {
+        visitWithItems(unPivotQuery.getWithItemsList(), context);
+
+        fromItemVisitor.visitFromItem(unPivotQuery.getFromItem(), context);
+        expressionVisitor.visitExpressions(unPivotQuery.getOnExpressions(), context);
+        expressionVisitor.visitExpressions(unPivotQuery.getValueColumns(), context);
+        return null;
+    }
+
     @Override
     public <S> T visit(FromQuery fromQuery, S context) {
         return null;

src/main/java/net/sf/jsqlparser/statement/select/UnPivotQuery.java

@@ -0,0 +1,115 @@
+/*-
+ * #%L
+ * JSQLParser library
+ * %%
+ * Copyright (C) 2004 - 2026 JSQLParser
+ * %%
+ * Dual licensed under GNU LGPL 2.1 or Apache License 2.0
+ * #L%
+ */
+package net.sf.jsqlparser.statement.select;
+
+import net.sf.jsqlparser.expression.Expression;
+import net.sf.jsqlparser.expression.operators.relational.ExpressionList;
+import net.sf.jsqlparser.schema.Column;
+
+/**
+ * DuckDB's simplified UNPIVOT statement:
+ * {@code UNPIVOT tbl ON columns [INTO NAME name VALUE values]}, the counterpart of
+ * {@link PivotQuery}.
+ *
+ * @see <a href="https://duckdb.org/docs/stable/sql/statements/unpivot">UNPIVOT</a>
+ */
+public class UnPivotQuery extends Select {
+    private FromItem fromItem;
+    private ExpressionList<Expression> onExpressions;
+    private String nameColumn;
+    private ExpressionList<Column> valueColumns;
+
+    public FromItem getFromItem() {
+        return fromItem;
+    }
+
+    public void setFromItem(FromItem fromItem) {
+        this.fromItem = fromItem;
+    }
+
+    public UnPivotQuery withFromItem(FromItem fromItem) {
+        setFromItem(fromItem);
+        return this;
+    }
+
+    public ExpressionList<Expression> getOnExpressions() {
+        return onExpressions;
+    }
+
+    public void setOnExpressions(ExpressionList<Expression> onExpressions) {
+        this.onExpressions = onExpressions;
+    }
+
+    public UnPivotQuery withOnExpressions(ExpressionList<Expression> onExpressions) {
+        setOnExpressions(onExpressions);
+        return this;
+    }
+
+    public String getNameColumn() {
+        return nameColumn;
+    }
+
+    public void setNameColumn(String nameColumn) {
+        this.nameColumn = nameColumn;
+    }
+
+    public UnPivotQuery withNameColumn(String nameColumn) {
+        setNameColumn(nameColumn);
+        return this;
+    }
+
+    public ExpressionList<Column> getValueColumns() {
+        return valueColumns;
+    }
+
+    public void setValueColumns(ExpressionList<Column> valueColumns) {
+        this.valueColumns = valueColumns;
+    }
+
+    public UnPivotQuery withValueColumns(ExpressionList<Column> valueColumns) {
+        setValueColumns(valueColumns);
+        return this;
+    }
+
+    @Override
+    public StringBuilder appendSelectBodyTo(StringBuilder builder) {
+        builder.append("UNPIVOT ").append(fromItem);
+        if (onExpressions != null) {
+            builder.append(" ON ").append(onExpressions);
+        }
+        if (nameColumn != null) {
+            builder.append(" INTO NAME ").append(nameColumn);
+            if (valueColumns != null) {
+                builder.append(" VALUE ").append(valueColumns);
+            }
+        }
+        return builder;
+    }
+
+    @Override
+    public <T, S> T accept(SelectVisitor<T> selectVisitor, S context) {
+        return selectVisitor.visit(this, context);
+    }
+
+    @Override
+    public <T, S> T accept(FromItemVisitor<T> fromItemVisitor, S context) {
+        return fromItemVisitor.visit(this, context);
+    }
+
+    @Override
+    public SampleClause getSampleClause() {
+        return null;
+    }
+
+    @Override
+    public FromItem setSampleClause(SampleClause sampleClause) {
+        return null;
+    }
+}

src/main/java/net/sf/jsqlparser/util/TablesNamesFinder.java

@@ -189,6 +189,7 @@
 import net.sf.jsqlparser.statement.select.ParenthesedSelect;
 import net.sf.jsqlparser.statement.select.Pivot;
 import net.sf.jsqlparser.statement.select.PivotQuery;
+import net.sf.jsqlparser.statement.select.UnPivotQuery;
 import net.sf.jsqlparser.statement.select.PivotVisitor;
 import net.sf.jsqlparser.statement.select.PivotXml;
 import net.sf.jsqlparser.statement.select.PlainSelect;
@@ -494,6 +495,20 @@ public <S> Void visit(PivotQuery pivotQuery, S context) {
         return null;
     }
 
+    @Override
+    public <S> Void visit(UnPivotQuery unPivotQuery, S context) {
+        visitWithItems(unPivotQuery.getWithItemsList(), context);
+        visitFromItem(unPivotQuery.getFromItem(), context);
+        visitExpressions(unPivotQuery.getOnExpressions(), context);
+        visitExpressions(unPivotQuery.getValueColumns(), context);
+        return null;
+    }
+
+    @Override
+    public void visit(UnPivotQuery unPivotQuery) {
+        SelectVisitor.super.visit(unPivotQuery);
+    }
+
     private <S> void visitSelectItems(List<? extends SelectItem<?>> selectItems, S context) {
         if (selectItems != null) {
             for (SelectItem<?> item : selectItems) {

src/main/java/net/sf/jsqlparser/util/deparser/SelectDeParser.java

@@ -63,6 +63,7 @@
 import net.sf.jsqlparser.statement.select.ParenthesedSelect;
 import net.sf.jsqlparser.statement.select.Pivot;
 import net.sf.jsqlparser.statement.select.PivotQuery;
+import net.sf.jsqlparser.statement.select.UnPivotQuery;
 import net.sf.jsqlparser.statement.select.PivotVisitor;
 import net.sf.jsqlparser.statement.select.PivotXml;
 import net.sf.jsqlparser.statement.select.PlainSelect;
@@ -436,6 +437,17 @@ private <S> void deparseFromClause(PlainSelect plainSelect, S context) {
     }
 
 
+    @Override
+    public <S> StringBuilder visit(UnPivotQuery unPivotQuery, S context) {
+        unPivotQuery.appendSelectBodyTo(builder);
+        return builder;
+    }
+
+    @Override
+    public void visit(UnPivotQuery unPivotQuery) {
+        SelectVisitor.super.visit(unPivotQuery);
+    }
+
     @Override
     public <S> StringBuilder visit(PivotQuery pivotQuery, S context) {
         List<WithItem<?>> withItemsList = pivotQuery.getWithItemsList();

src/main/java/net/sf/jsqlparser/util/validation/validator/SelectValidator.java

@@ -34,6 +34,7 @@
 import net.sf.jsqlparser.statement.select.ParenthesedSelect;
 import net.sf.jsqlparser.statement.select.Pivot;
 import net.sf.jsqlparser.statement.select.PivotQuery;
+import net.sf.jsqlparser.statement.select.UnPivotQuery;
 import net.sf.jsqlparser.statement.select.PivotVisitor;
 import net.sf.jsqlparser.statement.select.PivotXml;
 import net.sf.jsqlparser.statement.select.PlainSelect;
@@ -160,6 +161,14 @@ public <S> Void visit(PlainSelect plainSelect, S context) {
         return null;
     }
 
+    @Override
+    public <S> Void visit(UnPivotQuery unPivotQuery, S context) {
+        validateFeature(Feature.pivot);
+        validateOptionalFromItem(unPivotQuery.getFromItem());
+        validateOptionalExpressions(unPivotQuery.getOnExpressions());
+        return null;
+    }
+
     @Override
     public <S> Void visit(PivotQuery pivotQuery, S context) {
         if (isNotEmpty(pivotQuery.getWithItemsList())) {
@@ -464,6 +473,11 @@ public void visit(PivotQuery pivotQuery) {
         visit(pivotQuery, null);
     }
 
+    @Override
+    public void visit(UnPivotQuery unPivotQuery) {
+        visit(unPivotQuery, null);
+    }
+
     public void visit(SelectItem<?> selectExpressionItem) {
         visit(selectExpressionItem, null);
     }

src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt

@@ -6356,6 +6356,8 @@ Select Select() #Select:
             (
                 LOOKAHEAD(2) select = PivotQuery()
                 |
+                LOOKAHEAD(2) select = UnPivotQuery()
+                |
                 LOOKAHEAD(3) select = PlainSelect()
                 |
                 LOOKAHEAD(3) select = Values()
@@ -7728,6 +7730,28 @@ List<SelectItem<Function>> PivotFunctionItems():
     { return functionItems; }
 }
 
+/**
+ * DuckDB's simplified UNPIVOT statement:
+ * UNPIVOT tbl ON columns [INTO NAME name VALUE values].
+ */
+UnPivotQuery UnPivotQuery():
+{
+    UnPivotQuery unPivotQuery = new UnPivotQuery();
+    ExpressionList<Expression> onExpressions;
+    ExpressionList<Column> valueColumns;
+    FromItem fromItem;
+    String nameColumn;
+}
+{
+    <K_UNPIVOT> fromItem=FromItem() { unPivotQuery.setFromItem(fromItem); }
+    <K_ON> onExpressions=ExpressionList() { unPivotQuery.setOnExpressions(onExpressions); }
+    [
+        <K_INTO> <K_NAME> nameColumn=RelObjectName() { unPivotQuery.setNameColumn(nameColumn); }
+        <K_VALUE> valueColumns=ColumnList() { unPivotQuery.setValueColumns(valueColumns); }
+    ]
+    { return unPivotQuery; }
+}
+
 PivotQuery PivotQuery():
 {
     PivotQuery pivotQuery = new PivotQuery();

src/test/java/net/sf/jsqlparser/statement/select/DuckDBTest.java

@@ -603,4 +603,39 @@ void testBarePipeQueryStillParses() throws JSQLParserException {
         String sqlStr = "FROM t |> WHERE a > 1";
         TestUtils.assertSqlCanBeParsedAndDeparsed(sqlStr, true);
     }
+
+    @Test
+    void testUnPivotStatement() throws JSQLParserException {
+        String sqlStr = "UNPIVOT monthly_sales ON jan, feb INTO NAME month VALUE sales";
+        UnPivotQuery unPivotQuery =
+                (UnPivotQuery) TestUtils.assertSqlCanBeParsedAndDeparsed(sqlStr, true);
+
+        Assertions.assertEquals("month", unPivotQuery.getNameColumn());
+        Assertions.assertEquals(2, unPivotQuery.getOnExpressions().size());
+        Assertions.assertEquals(1, unPivotQuery.getValueColumns().size());
+    }
+
+    @Test
+    void testUnPivotStatementWithoutIntoClause() throws JSQLParserException {
+        String sqlStr = "UNPIVOT monthly_sales ON jan, feb";
+        UnPivotQuery unPivotQuery =
+                (UnPivotQuery) TestUtils.assertSqlCanBeParsedAndDeparsed(sqlStr, true);
+
+        Assertions.assertNull(unPivotQuery.getNameColumn());
+    }
+
+    @Test
+    void testUnPivotStatementTablesNamesFinder() throws JSQLParserException {
+        String sqlStr = "UNPIVOT ds.monthly_sales ON jan, feb INTO NAME month VALUE sales";
+
+        Assertions.assertEquals(java.util.Collections.singletonList("ds.monthly_sales"),
+                new net.sf.jsqlparser.util.TablesNamesFinder<Void>()
+                        .getTableList(net.sf.jsqlparser.parser.CCJSqlParserUtil.parse(sqlStr)));
+    }
+
+    @Test
+    void testUnPivotInFromClauseStillParses() throws JSQLParserException {
+        String sqlStr = "SELECT * FROM monthly_sales UNPIVOT (sales FOR month IN (jan, feb))";
+        TestUtils.assertSqlCanBeParsedAndDeparsed(sqlStr, true);
+    }
 }