what is the dependent subquery in MySql?

A dependent subquery in MySql is a subquery that relies on data from the outer query to execute. It cannot be executed independently and must be executed in conjunction with the outer query.

相关问题

What is the biggest advantage of implementing threads in user space? What is the biggest disadvantage?

The biggest advantage of implementing threads in user space is that it is faster and more efficient than kernel-level threads. User-level threads can be created and managed without the overhead of system calls, context switching, and other kernel-level operations.

The biggest disadvantage of implementing threads in user space is that they are not truly concurrent, as they are dependent on the scheduling of the underlying operating system. This can lead to issues with synchronization and resource sharing, as well as decreased performance in situations where there are many threads competing for resources. Additionally, user-level threads are not as well-suited for multi-processor systems, as they are not able to take full advantage of the available hardware.

dependent subquery

依赖子查询是一种SQL查询，其中内部查询依赖于外部查询的结果。内部查询必须在外部查询之前执行，并且返回的结果将用于外部查询的条件或操作中。依赖子查询通常用于复杂的查询，例如在多个表之间进行连接和过滤。