Usage of the substr function in the database: 1. [SUBSTR(str,pos,len)] intercepts len characters from the position starting from pos; 2. [SUBSTR(str,pos)] starts from the position of pos, Cut to the end.
Usage of substr function in database:
1, SUBSTR(str,pos,len)
: From the starting position of pos, intercept len characters
substr(string ,1,3) :取string左边第1位置起,3字长的字符串。
So the result is: str
substr(string, -1,3):取string右边第1位置起,3字长的字符串。显然右边第一位置起往右不够3字长。
The result can only be: g
substr(string, -3,3):取string右边第3位置起,3字长的字符串。
The result is: ing
2, SUBSTR(str,pos): The starting position of pos
, intercepted until the end
substr(string ,4) : 从右第4位置截取到最后
The result is: ing
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