The Employee table holds all employees including their managers. Every employee has an Id, and there is also a column for the manager Id.

Write a SQL query to find all duplicate emails in a table named Person.

Given a Weather table, write a SQL query to find all dates’ Ids with higher temperature compared to its previous (yesterday’s) dates.

Write a SQL query to delete all duplicate email entries in a table named Person, keeping only unique emails based on its smallest Id.

There is a table courses with columns: student and class

Given a table salary, such as the one below, that has m=male and f=female values. Swap all f and m values (i.e., change all f values to m and vice versa) with a...

PostgreSQL 使用 DROP TABLE 语句来删除表格，包含表格数据、规则、触发器等，所以删除表格要慎重，删除后所有信息就消失了。

在PCI总线中，所有需要提交中断请求的设备，必须能够通过INTx引脚提交中断请求，而MSI机制是一个可选机制。而在PCIe总线中，PCIe设备必须支持MSI或者MSI-X中断请求机制，而可以不支持INTx中断消息。...

一般嵌入式系统使用的都是对称多处理器（Symmetric Multi-Processor, SMP）系统，包含了多个cpu, 这几个cpu都是相同的处理器，如4核Contex-A53。但是在系统 启动阶段他们的地位并不是相同的，其中core0是主cpu（也叫引导处理器）,...

如果是CHAR，VARCHAR类型，length可以小于字段实际长度；如果是BLOB和TEXT类型，必须指定 length。