增加查询表格信息

chain.go

@@ -190,7 +190,9 @@ func (this *Query) GetTableInfo(table string) (map[string]interface{}, error) {
 		"IS_NULLABLE",    //是否为空
 	}
 	sql := "select `" + strings.Join(field, "`,`") + "` from information_schema.COLUMNS where table_name = ? and table_schema = ?"
-
+	if this.conn == nil {
+		this.conn = DB
+	}
 	stmtSql, err := this.conn.Prepare(sql)
 	if err != nil {
 		return nil, err