My curiosity always gets the best of me and I've searched online for an explanation to this and came up with nothing (could be because I didn't use the right terms.)
我的好奇心始终是我最好的，我在网上搜索了一个解释，并没有得到任何结果（可能是因为我没有使用正确的条款。）
Can someone please explain why SQL Server returns a value of zero (0) when the following is executed, instead of an empty string ('').
有人可以解释为什么SQL Server在执行以下操作时返回值为零（0），而不是空字符串（''）。
DECLARE @I AS INT
SET @I = NULL
SELECT ISNULL(@I, '') -- 0
2 个解决方案
#1
2
As declared here, the second argument to ISNULL is the replacement_value, which "must be of a type that is implicitly convertible to the type of check_expresssion." Implicitly converting '' to INT results in 0.
正如这里声明的那样，ISNULL的第二个参数是replacement_value，它“必须是一个可以隐式转换为check_expresssion类型的类型”。将''隐式转换为INT会导致0。
#2
2
Because @I is declared as an INT, the empty string is implicitly CAST as an integer resulting in a ZERO.
因为@I被声明为INT，所以空字符串隐式地CAST为整数，从而产生ZERO。
#1
2
As declared here, the second argument to ISNULL is the replacement_value, which "must be of a type that is implicitly convertible to the type of check_expresssion." Implicitly converting '' to INT results in 0.
正如这里声明的那样，ISNULL的第二个参数是replacement_value，它“必须是一个可以隐式转换为check_expresssion类型的类型”。将''隐式转换为INT会导致0。
#2
2
Because @I is declared as an INT, the empty string is implicitly CAST as an integer resulting in a ZERO.
因为@I被声明为INT，所以空字符串隐式地CAST为整数，从而产生ZERO。