Generate nullable subselect statements

internal/compiler/output_columns.go

@@ -344,6 +344,11 @@ func outputColumns(qc *QueryCatalog, node ast.Node) ([]*Column, error) {
 			if res.Name != nil {
 				first.Name = *res.Name
 			}
+
+			if hasWhereOrHavingClause(n) {
+				first.NotNull = false
+			}
+
 			cols = append(cols, first)
 
 		default:
@@ -633,3 +638,17 @@ func findColumnForRef(ref *ast.ColumnRef, tables []*Table, selectStatement *ast.
 
 	return nil
 }
+
+// hasWhereOrHavingClause returns true if the statement contains WHERE or HAVING clause
+func hasWhereOrHavingClause(node ast.Node) bool {
+	stmt := node.(*ast.SelectStmt)
+
+	if _, isTODO := stmt.WhereClause.(*ast.TODO); stmt.WhereClause != nil && !isTODO {
+		return true
+	}
+	if _, isTODO := stmt.HavingClause.(*ast.TODO); stmt.HavingClause != nil && !isTODO {
+		return true
+	}
+
+	return false
+}

internal/endtoend/testdata/nullable_subselect/mysql/query.sql

@@ -0,0 +1,7 @@
+CREATE TABLE foo (a int not null, b int);
+
+-- name: SubqueryWithWhereClause :many
+SELECT a, (SELECT COUNT(a) FROM foo WHERE a > 10) as "total" FROM foo;
+
+-- name: SubqueryWithHavingClause :many
+SELECT a, (SELECT COUNT(a) FROM foo GROUP BY b HAVING COUNT(a) > 10) as "total" FROM foo;

internal/endtoend/testdata/nullable_subselect/mysql/sqlc.json

@@ -0,0 +1,12 @@
+{
+  "version": "1",
+  "packages": [
+    {
+      "path": "go",
+      "engine": "mysql",
+      "name": "querytest",
+      "schema": "query.sql",
+      "queries": "query.sql"
+    }
+  ]
+}

internal/endtoend/testdata/nullable_subselect/postgresql/pgx/v4/query.sql

@@ -0,0 +1,7 @@
+CREATE TABLE foo (a int not null, b int);
+
+-- name: SubqueryWithWhereClause :many
+SELECT a, (SELECT COUNT(a) FROM foo WHERE a > 10) as "total" FROM foo;
+
+-- name: SubqueryWithHavingClause :many
+SELECT a, (SELECT COUNT(a) FROM foo GROUP BY b HAVING COUNT(a) > 10) as "total" FROM foo;

internal/endtoend/testdata/nullable_subselect/postgresql/pgx/v4/sqlc.json

@@ -0,0 +1,13 @@
+{
+  "version": "1",
+  "packages": [
+    {
+      "path": "go",
+      "engine": "postgresql",
+      "sql_package": "pgx/v4",
+      "name": "querytest",
+      "schema": "query.sql",
+      "queries": "query.sql"
+    }
+  ]
+}