diff --git a/advisor/heuristic.go b/advisor/heuristic.go
index 4d7087b38e44e4c3c0480b36c5a5c72172043618..e03ef1145a8ab7702630cd55f79f4d2ef1cc4e7d 100644
--- a/advisor/heuristic.go
+++ b/advisor/heuristic.go
@@ -261,7 +261,8 @@ func (idxAdv *IndexAdvisor) RuleImplicitConversion() Rule {
 				common.Log.Debug("DataType: `%s`.`%s` (%s) VS `%s`.`%s` (%s)",
 					colList[0].Table, colList[0].Name, type1,
 					colList[1].Table, colList[1].Name, type2)
-				if strings.ToLower(type1) != strings.ToLower(type2) {
+				// case-insensitive check type1, type2
+				if !strings.EqualFold(type1, type2) {
 					content = append(content, fmt.Sprintf("`%s`.`%s` (%s) VS `%s`.`%s` (%s) datatype not match",
 						colList[0].Table, colList[0].Name, type1,
 						colList[1].Table, colList[1].Name, type2))
@@ -296,6 +297,8 @@ func (idxAdv *IndexAdvisor) RuleImplicitConversion() Rule {
 				sqlparser.StrVal: {
 					"char", "varchar", "tinytext", "text", "mediumtext", "longtext",
 					"date", "time", "datetime", "timestamp", "year",
+					"tinyint", "smallint", "mediumint", "int", "integer", "bigint",
+					"float", "double", "real", "decimal",
 				},
 				sqlparser.IntVal: {
 					"tinyint", "smallint", "mediumint", "int", "integer", "bigint",
diff --git a/advisor/index_test.go b/advisor/index_test.go
index 6e755d843530f52c77b1fd8685806991dd3c3c19..53b061ed1bdee37c5c77bb6a4a9eb35aea1480b9 100644
--- a/advisor/index_test.go
+++ b/advisor/index_test.go
@@ -83,6 +83,7 @@ func TestRuleImplicitConversion(t *testing.T) {
 	}
 
 	sqls := [][]string{
+		// ARG.003
 		{
 			"SELECT * FROM t1 WHERE title >= 60;",
 			"SELECT * FROM t1, t2 WHERE t1.title = t2.title;",
@@ -90,11 +91,13 @@ func TestRuleImplicitConversion(t *testing.T) {
 			"SELECT * FROM t1 WHERE title in (60, '60');",
 			"SELECT * FROM t1 WHERE title in (60);",
 			"SELECT * FROM t1 WHERE title in (60, 60);",
-			"SELECT * FROM t4 WHERE col = '1'",
+			"SELECT * FROM t1 WHERE title = 1",
 		},
+		// OK
 		{
-			// https://github.com/XiaoMi/soar/issues/151
-			"SELECT * FROM t4 WHERE col = 1",
+			"SELECT * FROM t1 WHERE id = '1'", // string -> int can use index
+			"SELECT * FROM t1 WHERE id = 1",
+			"SELECT * FROM t4 WHERE col = 1", // https://github.com/XiaoMi/soar/issues/151
 			"SELECT * FROM sakila.film WHERE rental_rate > 1",
 		},
 	}
@@ -114,7 +117,7 @@ func TestRuleImplicitConversion(t *testing.T) {
 		if idxAdvisor != nil {
 			rule := idxAdvisor.RuleImplicitConversion()
 			if rule.Item != "ARG.003" {
-				t.Error("Rule not match:", rule, "Expect : ARG.003, SQL:", sql)
+				t.Error("Rule not match:", rule.Item, "Expect : ARG.003, SQL:", sql)
 			}
 		}
 	}
@@ -134,7 +137,7 @@ func TestRuleImplicitConversion(t *testing.T) {
 		if idxAdvisor != nil {
 			rule := idxAdvisor.RuleImplicitConversion()
 			if rule.Item != "OK" {
-				t.Error("Rule not match:", rule, "Expect : OK, SQL:", sql)
+				t.Error("Rule not match:", rule.Item, "Expect : OK, SQL:", sql)
 			}
 		}
 	}