SUBSTR(x,a,b)

SUBSTR(x,a,b) is a string function that outputs part of the character string x (string specification of length n). Only expressions that produce an alphanumeric value are permitted as string specification x. LOB values are allowed. If x is a LOB value, you must specify length b of the desired subarea.

a and b are expressions. The value b may not be larger than the column definition for a CHAR column.

SUBSTR(x,a,b)
x, a, b	Result of the SUBSTR(x,a,b) Function
`SUBSTR(x,a,b)`	Part of the character string `x` that starts at the `a`th character and is `b` characters long.
`SUBSTR(x,a)`	`SUBSTR(x,a,n-a+1)` supplies all of the characters in the character string `x` from the `a`th character to the last (`n`th) character.
`b` is an unsigned integer	`SUBSTR(x,a,b)` `b` can also have a value that is greater than `(n-a+1)`.
`b` is not an unsigned integer	`SUBSTR(x,a,b)` `b` may not exceed the value `(n-a+1)` .
`b>(n-a+1)`	`SUBSTR(x,a)` As many blanks (code attribute `ASCII`, `UNICODE`) or binary zeros (code attribute `BYTE`) are appended to the end of this result as are needed to give the result the length `b`.
`x`, `a` or `b` is a NULL value	`NULL` value

Example

SQL Tutorial, Functions, Changing character strings