摘要:
IFNULL() IFNULL(A,x):将A中为NULL的项换成x 示例: SELECT IFNULL( commission_pct, 0 ) AS sal FROM employees 条件查询 语法: 示例: 1, SELECT * FROM employees WHERE salary > 阅读全文
摘要:
concat():将若干字段连接并输出 示例 SELECT CONCAT( first_name, ' ',last_name ) AS 姓名 FROM employees NULL和任何字段拼接结果都为NULL 阅读全文