Underscore and NOT LIKE

You already know the percent sign

%

. Now we will complete your knowledge with the second wildcard - the underscore

_

- and with the negation of a pattern: NOT LIKE.

Underscore _ - exactly one character

The

_

character replaces exactly one arbitrary character (no more, no less):

1SELECT * FROM autorzy
2WHERE imie LIKE 'J_n';

This matches e.g. Jan, Jon - three letters, where the first is J, the last is n, and the middle one is arbitrary. It will not match Jaan (four letters) nor Jn (two letters), because each

_

is exactly one character.

Percent versus underscore

| Character | Meaning | |-----------|---------| |

%

| any sequence of characters (including empty) | |

_

| exactly one arbitrary character |

They can be combined, e.g.

'A_%'

means: starts with A, then exactly one arbitrary character, and then anything.

NOT LIKE - what does NOT match

To find rows that do not match the pattern, we use NOT LIKE:

1SELECT * FROM ksiazki
2WHERE tytul NOT LIKE 'O%';

This means: "Titles that do NOT start with the letter O". The

NOT

operator reverses the action of

LIKE

, just as it reversed an ordinary condition.

Thanks to

%

,

_

and

NOT LIKE

you have full control over pattern searching, @name. No scroll will hide from the eye of an experienced scribe!