# prefix_match and exact_match

> The `prefix_match` and `exact_match` predicates are used with Patricia trie indexes. They specify prefixes for string values in a `where` clause.

> For more details on the Patricia trie indexes and search methods, see the Patricia trie Indexes page.

> ## Syntax

>     select * from ... where s prefix_match '123'

>     select * from ... where s exact_match '123'

> ## Examples

>     create table T(s string);
>     create index idx_s on T(s) using ptree;
>     insert into T(s) values('123');
>     insert into T(s) values('12345678');
>     insert into T(s) values('111222333');

>     select * from T where s prefix_match '123';
>     s
>     ------------------------------------------------------------------------------
>     123
>     Selected records: 1

>     select * from T where s prefix_match '12345678';
>     s
>     ------------------------------------------------------------------------------
>     12345678
>     123
>     Selected records: 2

>     select * from T where s exact_match '123';
>     s
>     ------------------------------------------------------------------------------
>     123
>     12345678
>     Selected records: 2

>     select * from T where s exact_match '12345678';
>     s
>     ------------------------------------------------------------------------------
>     12345678
>     Selected records: 1