删除无用的连接操作之后的查询。
现在,有多少种方法可以用来执行这个连接操作?
确保查询中进行连接操作的列都有索引。
Ensure that columns that are joined in queries have indexes.
If you give me a number and a string, I'm going to concatenate them together, it's really different operations, but nonetheless, it's what it's going to do.
如果给的输入是一个数字和一个字符串,我将会把它们连接在一起,这实在是不正确的操作,但是无论如何,它就是会去这么做。
As we saw before, it simply concatenates them together and gives me back a longer string.
和我们之前学过的一样,这个操作会把两个字符串连接起来。
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