mysql的sql语句特殊处理语句总结(必看)

1、更新整张表，如果某一行数据的某一列的值为空，那么让他和另一列字段的值相等

UPDATE ot_tgbz set update_day=if(update_day is null,date,update_day);

2、更新整张表，如果某个字段大于2，那么把他们都更新成2；

UPDATE ot_user set xingyun_num=if(xingyun_num > 2,2,xingyun_num);

3、把shop_goods这个表里的thumb字段里的内容中含有https://www.jb51.net/的网址全部替换成空的。

update shop_goods  set thumb= replace (thumb,'https://www.jb51.net/','') where thumb like '％https://www.jb51.net/％';

4、sql语句多字段where查询

$map= " CAST(
 `UE_account` AS CHAR CHARACTER
    SET utf8
 ) LIKE '％$data％'
 OR CAST(
   `UE_accName` AS CHAR CHARACTER
   SET utf8
 ) LIKE '％$data％'
 OR CAST(
   `UE_truename` AS CHAR CHARACTER
   SET utf8
 ) LIKE '％$data％'
 OR CAST(
   `UE_phone` AS CHAR CHARACTER
   SET utf8
 ) LIKE '％$data％'";