mysql添加数据之前判断是否存在

示例：

 INSERT INTO tb_news_topic(title,summary) SELECt '218', 
'XQ33019920170811142528217' FROM DUAL WHERe NOT EXISTS(SELECt * 
FROM tb_news_topic WHERe title = '111')

语法：

INSERT INTO table(field1, field2, fieldn) SELECt 'field1', 
'field2', 'fieldn' FROM DUAL WHERe NOT EXISTS(SELECt field FROM 
table WHERe field = ?)

批量操作:
通过foreach遍历数组的时候，foreach里面不能使用await ，所在这个地方我用的for循环对数组进行遍历

for (let i = 0; i < list.data.length;i++){
    let sql = `INSERT INTO tb_news_topic(title,summary,url,topic_order,publishDate,createdAt) SELECt ?, 
?,?,?,?,? FROM DUAL WHERe NOT EXISTS(SELECt * 
FROM tb_news_topic WHERe title = ?)`
      // 直接执行sql语句
      const results = await this.app.mysql.query(sql, [list.data[i].title, 
        list.data[i].summary, 
        '',
        list.data[i].order, 
        new Date(list.data[i].publishDate), 
        this.app.mysql.literals.now,//当前时间
        list.data[i].title
      ]);
 }