Add select statement as possible operand in expressions

src/parser/bison_parser.y

@@ -612,6 +612,7 @@ operand:
 	|	unary_expr
 	|	binary_expr
 	|	function_expr
+	|	'(' select_no_paren ')' { $$ = Expr::makeSelect($2); }
 	;
 
 scalar_expr:

src/sql/Expr.cpp

@@ -102,6 +102,12 @@ namespace hsql {
     return e;
   }
 
+  Expr* Expr::makeSelect(SelectStatement* select) {
+    Expr* e = new Expr(kExprSelect);
+    e->select = select;
+    return e;
+  }
+
   bool Expr::isType(ExprType e_type) {
     return e_type == type;
   }

src/sql/Expr.h

@@ -6,6 +6,7 @@
 #include <vector>
 
 namespace hsql {
+  class SelectStatement;
 
   // Helper function used by the lexer.
   // TODO: move to more appropriate place.
@@ -19,7 +20,8 @@ namespace hsql {
     kExprPlaceholder,
     kExprColumnRef,
     kExprFunctionRef,
-    kExprOperator
+    kExprOperator,
+    kExprSelect
   };
 
   typedef struct Expr Expr;
@@ -66,6 +68,7 @@ namespace hsql {
     Expr* expr;
     Expr* expr2;
     std::vector<Expr*>* exprList;
+    SelectStatement* select;
     char* name;
     char* table;
     char* alias;
@@ -77,6 +80,7 @@ namespace hsql {
     char opChar;
     bool distinct;
 
+
     // Convenience accessor methods.
 
     bool isType(ExprType e_type);
@@ -117,6 +121,8 @@ namespace hsql {
     static Expr* makeFunctionRef(char* func_name, std::vector<Expr*>* exprList, bool distinct);
 
     static Expr* makePlaceholder(int id);
+
+    static Expr* makeSelect(SelectStatement* select);
   };
 
 // Zero initializes an Expr object and assigns it to a space in the heap

test/select_tests.cpp

@@ -157,3 +157,30 @@ TEST(SelectBetweenTest) {
 
   delete result;
 }
+
+TEST(SelectConditionalSelectTest) {
+  TEST_PARSE_SINGLE_SQL(
+    "SELECT * FROM t WHERE a = (SELECT MIN(v) FROM tt);",
+    kStmtSelect,
+    SelectStatement,
+    result,
+    stmt);
+
+  Expr* where = stmt->whereClause;
+  ASSERT_NOTNULL(where);
+  ASSERT(where->isType(kExprOperator));
+  ASSERT(where->isSimpleOp('='));
+
+  ASSERT_NOTNULL(where->expr);
+  ASSERT_STREQ(where->expr->getName(), "a");
+  ASSERT(where->expr->isType(kExprColumnRef));
+
+  ASSERT_NOTNULL(where->expr2);
+  ASSERT(where->expr2->isType(kExprSelect));
+
+  SelectStatement* select2 = where->expr2->select;
+  ASSERT_NOTNULL(select2);
+  ASSERT_STREQ(select2->fromTable->getName(), "tt")
+
+  delete result;
+}