mysql IFNULL函数简介 MySQL IFNULL函数是MySQL控制流函数之一，它接受两个参数，如果不是NULL，则返回第一个参数。 否则，IFNULL函数返回第二个参数。
I am trying to use test-driven development for an application that has to read a lot of data from disk. The problem is that the data is organized on the filesystem in a somewhat complex directory stru
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