first commit

common/tool/placeholders.go

@@ -0,0 +1,15 @@
+package tool
+
+import "strings"
+
+//替换
+func InPlaceholders(n int) string {
+	var b strings.Builder
+	for i := 0; i < n-1; i++ {
+		b.WriteString("?,")
+	}
+	if n > 0 {
+		b.WriteString("?")
+	}
+	return b.String()
+}