-纯碎个人记录,非喜勿喷 MySQL DELETE语句起别名报错问题 问题一 刷Leetcode的时侯写了这样一个SQL: DELETE from person p0 where p0.id in( SELECT p1.id from person p1,person p2
where p1.email = p2.email
and p1.id > p2.id
) Error : You have an erro...
原表如下: with t1 as( select 1 as id, "a,b" as course union select 2 as id, "a,b,c" as course union select 3 as id, null as course union select 4 as id, "c" as course
)
select * from t1; idcourse1a,b2a,b,c3NULL4c
需要将 cou...
Pikachu靶场中SQL注入 1.Pikachu(皮卡丘)靶场中SQL注入1.1.数字型注入1.2.字符型注入1.3.搜索型注入1.4.xx型注入1.5.insert/update注入1.6.delete注入1.7.http头注入1.8.盲注(base on boolian)1.9.盲注(base on time)1.10.宽字节注入 1.Pikachu(皮卡丘)靶场中SQL注入 ??若遇...
物化表 首先提出一个不相关的IN子查询 SELECT * FROM s1 WHERE key1 IN (SELECT common_field FROM s2 WHERE key3 = 'a'); 对于不相关的 IN 子查询来说,如果子查询的结果集中的记录条数很少,那么把子查询和外层 查询分别看成两个单独的单表查询效...
MySQL中索引的创建有三种方法,索引的删除有两种方法。 一、创建索引 (1)使用create index # 1.创建普通索引
create index 索引名 on 表名 (列名[(限制索引长度)]);
# 2.创建唯一性索引
create unique index 索引名 on 表名 (列名);
# 3.创建全文索引
c...
添加字段(可重复执行):
DROP PROCEDURE IF EXISTS add_column_acl_class_copy1;
DELIMITER $$
CREATE PROCEDURE add_column_acl_class_copy1() BEGIN IF NOT EXISTS (SELECT 1 FROM information_schema.columns WHERE table_name = 'acl_class...