substring function--sql

--substring (expression, start, length)expression to intercept the beginning of the intercept position of the starting subscript length to intercept--The subscript for the first character on the left is 1, for example, to intercept the character a, and to intercept a length starting with the first character.Select substring('ABCD',1,1)--if your starting position subscript is written in 0, then the Intercept character a will write the length 2Select substring('ABCD',0,2)--if your starting position subscript is 1, then the Intercept character a will write the length 3Select substring('ABCD',-1,3)     --In turn ...