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PREFIX
Syntax
PREFIX
Returns the substring of a character string, starting from the position specified by start_pos
and ending before the specified character.
PREFIX ( char_expression , start_pos , char_expression )
char_expression
Evaluates to a character string, typically a character-string literal or column name. If the
expression evaluates to NULL, PREFIX returns NULL.
start_pos
Evaluates to an integer value. PREFIX searches the string specified in the first argument
starting at that position. A value of 1 indicates the first character of the string.
char_expression
Evaluates to a single character. PREFIX returns the substring that ends before that
character. If PREFIX does not find the character, it returns the substring beginning at
start_pos, to the end of the string. If the expression evaluates to more than one character,
PREFIX ignores all but the first character.
Example The following example shows one way to use the PREFIX function:
create table prefix_table
(
colstring varchar(20),
colchar char(1)
);
insert into prefix_table values ('string.with.dots', '.');
insert into prefix_table values ('string-with-dashes', '-');
select colstring, colchar, prefix(colstring, 1, '.') from prefix_table;
COLSTRING COLCHAR prefix(COLSTRING,1,.)
--------------------- --------------------- ----------------------
string.with.dots . string
string-with-dashes - string-with-dashes
select colstring, colchar, prefix(colstring, 1, colchar) from prefix_table;
COLSTRING COLCHAR prefix(COLSTRING,1,COLCHAR)
--------------------- --------------------- ----------------------------
string.with.dots . string
string-with-dashes - string
select colstring, colchar, prefix(colstring, 1, 'X') from prefix_table;
COLSTRING COLCHAR prefix(COLSTRING,1,X)
--------------------- --------------------- ----------------------
string.with.dots . string.with.dots
string-with-dashes - string-with-dashes
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