摘要：
window.console = window.console || (function () { var c = {}; c.log = c.warn = c.debug = c.info = c.error = c.time = c.dir = c.profile= c.clear = c.ex 阅读全文
摘要：
select concat('大','小') as size from 表 查询出结果为：大小 select concat('大',NULL) as size from 表 查询出结果为：null concat中又一个参数为NULL，查出来的就为NULL select concat_ws('_',' 阅读全文