如何在查询中的变量名称周围添加双引号？

Question

如何在字符串变量周围添加引号？我的数据库执行查询，如果""是变量名，我该怎么办？我做了这个"+"+ School_name+"+"，但它不起作用如何我用引号添加变量名？

       Bundle bundle = this.getIntent().getExtras();
        School_name = bundle.getString("Serachvalue");



             db.selectQuery("SELECT * FROM uss_school sch LEFT JOIN uss_school_to_level sl ON  
    sch.school_id = sl.school_id LEFT JOIN uss_level l ON sl.level_id = l.level_id WHERE  
   l.title  ="+ School_name+" ORDER BY sch.name ASC");

但是数据库用引号执行wuery，

         SELECT * FROM uss_school sch LEFT JOIN uss_school_to_level sl ON sch.school_id =  
                  sl.school_id LEFT JOIN uss_level l ON sl.level_id
= l.level_id WHERE l.title = "Elementary" ORDER BY sch.name ASC

Answer 1

尝试以下方式，

db.selectQuery("SELECT * FROM uss_school sch LEFT JOIN uss_school_to_level sl ON  
    sch.school_id = sl.school_id LEFT JOIN uss_level l ON sl.level_id = l.level_id WHERE  
   l.title  ='"+ School_name+"' ORDER BY sch.name ASC");

只要在查询字段中使用字符串变量，就需要添加'。