Substr and substring function usage in SQL

About substr and substring The difference between

First, declare ,substr() Is based on Oracle Of ,substring() Is based on SQL Server Of , Remember not to mix , Otherwise, an error will be reported ！

MySQL: SUBSTR( ), SUBSTRING( )
Oracle: SUBSTR( )
SQL Server: SUBSTRING( )

1、Oracle Of substr

stay plsql in substr Is a separate function , String index with 1 Start .
grammar :

  substr( string, start_position, [ length ] )

If start_position yes 0,substr Or do you think so 1 Start .
If start_position Positive number ,substr With start_position Start calculating , contain start_position.
If start_position It's a negative number , From string Start counting forward at the end .
length, Returns the length of the string , If it's a negative number , return NULL.

Example ：

  substr('This is a test', , 2) would return 'is'
  substr('This is a test', 6) would return 'is a test'
  substr('TechOnTheNet', 1, 4) would return 'Tech'
  substr('TechOnTheNet', -3, 3) would return 'Net'
  substr('TechOnTheNet', -6, 3) would return 'The'
  substr('TechOnTheNet', -8, 2) would return 'On'

2、javascript Medium substr and substring Two methods

stay javascript There is substr and substring Two methods , The index of the string is in 0 Start .
grammar ：
substring Method is used to extract characters that are mediated between two specified subscripts .

stringObject.substring(start,stop)

explain ：
substring The substring returned by the method includes start The character at , But does not include end The character at .
If start And end equal , Then the method returns an empty string （ The length is 0 String ）.
If start Than end Big , Then the method will exchange these two parameters before extracting the substring .
If start or end It's a negative number , It will be replaced by 0.

substr Method is used to return a substring of a specified length starting at a specified position .

stringObject.substr(start [, length ])

explain ：
If length by 0 Or negative numbers , Will return an empty string .
If the parameter is not specified , Then the substring will continue to stringObject Last .

Example ：

   "0123456789".substring(5) return "56789"
   "0123456789".substring(0,5) return "01234"
   "0123456789".substring(2,0) return "01"
   "0123456789".substring(-1,5) return "01234"
 
   "0123456789".substr(5) return "56789"
   "0123456789".substr(2,0) return ""
   "0123456789".substr(2,2) return "23"  
   "0123456789".substr(-1,5) return "01234"   

3、java in substring yes string Object function

java in substring yes string Object function , Return to the location of String Object at the specified position . The index is from 0 Start calculation .
grammar ：

strVariable.substring(start[,end])  

substring Methods use start and end The smaller value of both is used as the starting point of the substring .strvar.substring(0,3) and strvar.substring(3, 0) Will return the same substring .
contain start The value of the location , It doesn't contain end The value of the location .

Example ：

"05718888888".substring(0,4) returns "0571"
"hamburger".substring(4, returns "urge"
"smiles".substring(1, 5) returns "mile"

4、 summary ：

except Oracle Of substr With 1 Index by string , The other two languages are based on 0 Action index .
java Of substring And javascript Of substring be similar .
javascript Of substr And Oracle/PLSQL Of substr be similar .

The source of the original text is ：http://jw1314.iteye.com/blog/1211431