工作中用到的sql

两列都相同去重

$sql = "select * from `bed_user` a where not exists(select 1 from `bed_user` where a.longitude=longitude and a.latitude=latitude and a.id<>id)";

update left join

UPDATE schools_2016 AS a LEFT OUTER JOIN school_rank_2015_airay AS b ON a.school_name = b.school_name SET a.rank = b.rank WHERE 1

删除最后一个字符

UPDATE schools_2016 set location = left(location,CHAR_LENGTH(location)-1) WHERE RIGHT(location,1)='市'

删除指定字符

UPDATE `schools_2016` SET `type`= trim(trailing '院校' from `type`) WHERE `type` LIKE '%院校'

导出数据表到csv文件

SELECT order_id,product_name,qty FROM orders WHERE foo = 'bar' INTO OUTFILE '/tmp/orders.csv' FIELDS TERMINATED BY ',' ENCLOSED BY '"' LINES TERMINATED BY '\n';

导出到csv（带headers）

SELECT 'Id','PostId','Score','Text','CreationDate','UserId'
UNION ALL
SELECT Id, PostId, Score,Text, CreationDate,UserId
from comments
into outfile '/tmp/comments.csv'
fields terminated by ','
enclosed by '"'
escaped by '"'
lines terminated by '\n';