SQL字符串拼接

①CONCAT() 拼接字符串基本型：SELECT CONCAT ( lastname , firstname) AS student_name FROM kalacloud_student;

②使用空格拼接字符串：仍然使用 SELECT CONCAT() 命令，空格需要使用' ' 两个单引号引起来。SELECT CONCAT(firstname, ' ', subject) AS studentDetail FROM kalacloud_student;

③使用特殊符号拼接字符串：SELECT CONCAT(firstname, '-', subject, '-', qualification)  AS detail FROM kalacloud_student;

④在筛选查询中进行字符串拼接并显示在表格里：SELECT CONCAT(qualification, ' ', firstname, ' - ', subject)  AS 候选人资料, wechat_id, phone FROM kalacloud_student WHERE qualification = 'MPhil';

⑤字符串与中文文本的拼接：SELECT CONCAT('候选人：', lastname,firstname, ' 学科：',subject,' 学历：', qualification) AS 简历 FROM kalacloud_student ORDER BY qualification DESC;

⑥CONCAT_WS() 仅需写一次分隔符即可拼接所有字符串：SELECT CONCAT_WS(' / ', firstname, phone, subject, qualification) AS Detail FROM kalacloud_student;

总结：CONCAT() 字符串拼接功能在日常工作场景中使用非常频繁，但它的原理很好理解。任何非数据库中的字符串都加上' 单引号引起来即可。