SQL SUBSTRING 与 RIGHT - 最佳实践
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SQL SUBSTRING vs RIGHT - Best Practice
提问by John
I'm trying to find out the best practice when removing characters from the start of a string.
我试图找出从字符串开头删除字符时的最佳实践。
In some languages, you can use MID without a length parameter however, in TSQL the length is required.
在某些语言中，您可以使用不带长度参数的 MID，但是，在 TSQL 中需要长度。
Considering the following code, what is the best practise? (The hex string is variable length)
考虑以下代码，最佳实践是什么？（十六进制字符串是可变长度的）
DECLARE @sHex VARCHAR(66)
SET @sHex = '0x7E260F3DA734AD4BD816B88F485CE501D843DF067C8EDCB8AC7DAD331852E04D'
PRINT RIGHT(@sHex,LEN(@sHex) -2)
PRINT SUBSTRING(@sHex,3,LEN(@sHex) -2)
PRINT SUBSTRING(@sHex,3,65535)
采纳答案by Marc Gravell
Well, the first is more expressive of your intent. The last is clearly messy (hard-coded length etc). I doubt you'd find much performance difference between the first & second, so I'd use the simplest - RIGHT.
嗯，第一个更能表达你的意图。最后一个显然是混乱的（硬编码长度等）。我怀疑您会发现第一个和第二个之间的性能差异很大，所以我会使用最简单的 - RIGHT.
Of course, if you are doing this lots, you could write a udf that encapsulates this - then if you change your mind you only have one place to change...
当然，如果你做了这么多，你可以写一个 udf 来封装这个——然后如果你改变主意，你只有一个地方可以改变......
回答by SQLMenace
+1 on the right function, it is much clearer what you want to do
+1在正确的功能上，你想做什么就更清楚了
回答by Andrew Hare
I would use the rightfunction as it better shows your intent. The substringfunction is best used for extracting strings from the middle of a longer string.
我会使用该right功能，因为它可以更好地显示您的意图。该substring函数最适用于从较长字符串的中间提取字符串。
回答by Yada
I use the second SUBSTRING because it is more portable. Not all dbms had LEFT and RIGHT.
我使用第二个 SUBSTRING 是因为它更便携。并非所有 dbms 都有 LEFT 和 RIGHT。
