如果存在另一个表，则在SQLite中创建临时表

问题描述

我需要在SQLite数据库中创建一个临时表(这是Employees表的副本)，前提是存在名为"Employees"的表.员工表中只有两列-EmployeeId(整数)和EmployeeName(varchar(100)).

I need to create a temp table (which is a copy of Employees table) in a SQLite database, provided the table by the name of 'Employees' exists. There are only 2 columns in Employees table - EmployeeId (integer) and EmployeeName (varchar(100)).

有什么方法可以使用SQLite SQL来实现上述目的?

预期的SQL伪代码如下所示，该伪代码在SQlite中不起作用.我希望它能像下面的SQLite中的伪代码一样强大.

Pseudo-code for intended SQL, which does not work in SQlite is as below. I hope there was something as powerful as the pseudo-code below in SQLite.

--if Employees table exists then create a temp table and populate it with all
--rows from Employees table
CREATE TEMP TABLE tempEmployees if exists Employees as select *  from Employees;

推荐答案

SQLite几乎没有控制逻辑.作为嵌入式数据库，它被设计为与真实"编程语言一起使用.

SQLite has almost no control logic; as an embedded database, it is designed to be used together with a 'real' programming language.

您可以尝试复制数据，然后忽略错误:

You could just try to copy the data, and ignore the errors:

try:
    c.execute("CREATE TEMP TABLE tempEmployees AS SELECT * FROM Employees")
except:
    pass

但是，这还将消除其他任何错误.

However, this would also suppress any other errors.

一个更好的主意是显式检查表是否存在:

A better idea is to check explicitly whether the table exists:

c.execute("SELECT 1 FROM sqlite_master WHERE type='table' AND name='Employees'")
if c.fetchone():
    c.execute("CREATE TEMP TABLE tempEmployees AS SELECT * FROM Employees")

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