diff --git a/src/sql/engine/expr/ob_expr_find_in_set.cpp b/src/sql/engine/expr/ob_expr_find_in_set.cpp
index 6df485581f..4ac048b6e0 100644
--- a/src/sql/engine/expr/ob_expr_find_in_set.cpp
+++ b/src/sql/engine/expr/ob_expr_find_in_set.cpp
@@ -77,10 +77,13 @@ int search(const ObString &str, const ObString &str_list, const ObCollationType
     ObString comma_str = ObCharsetUtils::get_const_str(cs_type, ',');
 
     while (str_list_pos < str_list.length()) {
-      int64_t comma_pos = ObCharset::instrb(cs_type, str_list.ptr() + str_list_pos, str_list.length() - str_list_pos,
-                                            comma_str.ptr(), comma_str.length());
+      comma_pos = ObCharset::instrb(cs_type,
+                                    str_list.ptr() + str_list_pos,
+                                    str_list.length() - str_list_pos,
+                                    comma_str.ptr(),
+                                    comma_str.length());
       const char* elem_ptr = str_list.ptr() + str_list_pos;
-      int64_t elem_length = (comma_pos >=0) ? comma_pos : str_list.length() - str_list_pos;
+      int64_t elem_length = (comma_pos >= 0) ? comma_pos : (str_list.length() - str_list_pos);
       if (0 != ObCharset::strcmp(cs_type, elem_ptr, elem_length, str.ptr(), str.length())) {
         //not match
         str_list_pos += elem_length + ((comma_pos >= 0) ? comma_str.length() : 0);
@@ -90,7 +93,8 @@ int search(const ObString &str, const ObString &str_list, const ObCollationType
       }
     }
 
-    if (str_list_pos < str_list.length()) {
+    if (str_list_pos < str_list.length()
+        || (str_list_pos == str_list.length() && 0 == str.length() && comma_pos > 0)) {
       res_pos = elem_idx;
     } else {
       res_pos = 0;
diff --git a/src/sql/engine/expr/ob_expr_func_sleep.cpp b/src/sql/engine/expr/ob_expr_func_sleep.cpp
index 56aeb49bd9..d265d969e6 100644
--- a/src/sql/engine/expr/ob_expr_func_sleep.cpp
+++ b/src/sql/engine/expr/ob_expr_func_sleep.cpp
@@ -110,6 +110,9 @@ int ObExprSleep::eval_sleep(const ObExpr &expr, ObEvalCtx &ctx, ObDatum &res)
   if (OB_FAIL(expr.eval_param_value(ctx, sec))) {
     LOG_WARN("eval arg failed", K(ret));
   } else if (sec->is_null()) {
+    ret = OB_INVALID_ARGUMENT;
+    LOG_USER_ERROR(OB_INVALID_ARGUMENT, "sleep");
+    LOG_WARN("invalid arguments to sleep");
   } else if (OB_FAIL(get_usec(number::ObNumber(sec->get_number()), usec, calc_alloc))) {
     ret = OB_SUCCESS;
   } else {
diff --git a/src/sql/resolver/expr/ob_raw_expr_resolver_impl.cpp b/src/sql/resolver/expr/ob_raw_expr_resolver_impl.cpp
index e6f9f9cbd8..5c1573cef8 100644
--- a/src/sql/resolver/expr/ob_raw_expr_resolver_impl.cpp
+++ b/src/sql/resolver/expr/ob_raw_expr_resolver_impl.cpp
@@ -2548,9 +2548,9 @@ int ObRawExprResolverImpl::process_datatype_or_questionmark(const ParseNode &nod
           ret = OB_NOT_INIT;
           LOG_WARN("context param list is null", K(ret));
         } else if (val.get_unknown() >= ctx_.param_list_->count()) {
-          ret = OB_ERR_UNEXPECTED;
-          LOG_WARN("question mark index out of param list count",
-                   "index", val.get_unknown(), "param_count", ctx_.param_list_->count());
+          ret = OB_ERR_BIND_VARIABLE_NOT_EXIST;
+          LOG_WARN("bind variable does not exist",
+                   K(ret), K(val.get_unknown()), K(ctx_.param_list_->count()));
         } else {
           const ObObjParam &param = ctx_.param_list_->at(val.get_unknown());
           c_expr->set_is_literal_bool(param.is_boolean());