Web而not extsts 的子查询依然能用到表上的索引。所以无论那个表大,用not exists 都比not in 要快。 ===== 系统要求进行SQL优化,对效率比较低的SQL进行优化,使其运行效率更高,其中要求对SQL中的部分in/not in修改为exists/not exists. 修改方法如下: in的SQL语句 WebSep 28, 2024 · 必知必会——关于SQL中的NOT IN优化. 如果您使用 SELECT…WHERE x NOT IN(SELECT y FROM…)等“ NOT IN”编写SQL查询,必须了解当“ x”或“ y”为NULL时会发生什 …
MySQL AND, OR and NOT Operators - W3School
Webmysql 中的 in 运算符用来判断表达式的值是否位于给出的列表中;如果是,返回值为 1,否则返回值为 0。 not in 的作用和 in 恰好相反,not in 用来判断表达式的值是否不存在于给出的列表中;如果不是,返回值为 1,否则返回值为 0。 in 和 not in 的语法格式如下: WebMay 6, 2024 · MySQL重建主键Id #清除主键 ALTER TABLE [table_name] DROP id; #重新生成 ALTER TABLE [table_name] ADD id INT NOT NU nav of nippon india large cap fund
让MySQL速度提升3倍的19种优化方式 - 腾讯云开发者社区-腾讯云
WebWhen the where clause is used with the NOT IN keyword in the MySQL statement, it does not affect the rows that do not matches with the values that are provided to the NOT IN function as arguments. Examples of MySQL NOT IN. To know the concept of mysql NOT IN function, we will create table named “students”. Below is query for create ... WebMysql 中 not in 的查询优化. 最近做性能优化时,通过开启 MySQL 的慢日志查询配置,发现 有一条慢sql,在这里记录下分析和优化的过程。. select id from fucdn_customer_domain where id not in ( select customer_domain_id from fucdn_customer_domain_cache where cache_time > 0 ) and status = 1. 可以看出 ... WebAug 19, 2024 · Example of MySQL NOT IN using two tables . If you want to fetch those rows from the table book_mast which does not contain those pub_id's which are not exist in publisher table, the following sql can be used. Code: SELECT * FROM book_mast WHERE pub_id NOT IN( SELECT pub_id FROM publisher); Sample Output: nav of mutual funds historical data