Improve SimpleExpression.in(...) signature

querydsl-core/src/main/java/com/querydsl/core/types/dsl/Expressions.java

@@ -1263,6 +1263,33 @@ public final class Expressions {
         return rv;
     }
 
+
+    /**
+     * Combine the given expressions into a list expression
+     *
+     * @param clazz type of list expression
+     * @param exprs list elements
+     * @return list expression
+     */
+    @SuppressWarnings("unchecked")
+    public static <T> Expression<T> list(Class<T> clazz, Expression<?>... exprs) {
+        Expression<T> rv = (Expression<T>) exprs[0];
+        for (int i = 1; i < exprs.length; i++) {
+            rv = new SimpleOperation<T>(clazz, Ops.LIST, rv, exprs[i]);
+        }
+        return rv;
+    }
+
+    /**
+     * Combine the given expressions into a list expression
+     *
+     * @param exprs list elements
+     * @return list expression
+     */
+    public static Expression<Tuple> list(Expression<?>... exprs) {
+        return list(Tuple.class, exprs);
+    }
+
     /**
      * Create a null expression for the specified type
      *

querydsl-core/src/main/java/com/querydsl/core/types/dsl/SimpleExpression.java

@@ -229,6 +229,16 @@ public abstract class SimpleExpression<T> extends DslExpression<T> {
         return Expressions.booleanOperation(Ops.IN, mixin, right);
     }
 
+    /**
+     * Create a {@code this in right} expression
+     *
+     * @param right rhs of the comparison
+     * @return this in right
+     */
+    public BooleanExpression in(Expression<? extends T>... right) {
+        return Expressions.booleanOperation(Ops.IN, mixin, Expressions.list(right));
+    }
+
     /**
      * Create a {@code this <> right} expression
      *

querydsl-sql/src/main/java/com/querydsl/sql/SQLSerializer.java

@@ -890,7 +890,13 @@ public class SQLSerializer extends SerializerBase<SQLSerializer> {
             }
         }
 
-        if (operator == SQLOps.UNION || operator == SQLOps.UNION_ALL) {
+        if (operator == Ops.LIST && args.get(0) instanceof SubQueryExpression) {
+            boolean oldUnion = inUnion;
+            inUnion = true;
+            super.visitOperation(type, SQLOps.UNION, args);
+            inUnion = oldUnion;
+
+        } else if (operator == SQLOps.UNION || operator == SQLOps.UNION_ALL) {
             boolean oldUnion = inUnion;
             inUnion = true;
             super.visitOperation(type, operator, args);

querydsl-sql/src/test/java/com/querydsl/sql/SelectBase.java

@@ -895,6 +895,17 @@ public class SelectBase extends AbstractBaseTest {
         assertEquals(0, query().from(employee).where(employee.id.in(ImmutableList.<Integer>of())).fetchCount());
     }
 
+    @Test
+    @ExcludeIn({MYSQL, TERADATA})
+    public void in_subqueries() {
+        QEmployee e1 = new QEmployee("e1");
+        QEmployee e2 = new QEmployee("e2");
+        assertEquals(2, query().from(employee).where(employee.id.in(
+            query().from(e1).where(e1.firstname.eq("Mike")).select(e1.id),
+            query().from(e2).where(e2.firstname.eq("Mary")).select(e2.id)
+        )).fetchCount());
+    }
+
     @Test
     public void notIn_empty() {
         long count = query().from(employee).fetchCount();