concat()用法

  

SELECT school_code,`name`,phone from student WHERE login_name REGEXP 'ning$'LIMIT 10;

concat()

• SELECT CONCAT(school_code,`name`) from student WHERE login_name REGEXP 'ning$' LIMIT 10;

• SELECT CONCAT(school_code,`name`,phone) from student WHERE login_name REGEXP 'ning$' LIMIT 10;（有一个字段是null，concat的结果是null）

  CONCAT_WS()

• SELECT CONCAT_WS('-',school_code,NAME,login_name,phone) from student WHERE login_name REGEXP 'ning$' LIMIT 10;

• SELECT `name`,MIN(id) FROM student GROUP BY `name` HAVING COUNT(id) >=2 LIMIT 10;

 GROUP_CONCAT()

• SELECT id,`name` from student WHERE `name`='刘媛媛' LIMIT 10;

• SELECT NAME,GROUP_CONCAT(id) from student WHERE `name`='刘媛媛' LIMIT 10;

• SELECT NAME,GROUP_CONCAT(id) FROM student GROUP BY `name` HAVING COUNT(id) >=2 LIMIT 10;