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The LIKE Predicate


A LIKE predicate compares the value in a string expression with a character string pattern which may contain wildcard characters (meta-characters).

It has the form:

The string-value on the left hand side of the LIKE operator must be a string expression.

The character-pattern on the right hand side of the LIKE operator is a string expression that can be specified as a string literal or by using a host variable.

The following meta-characters (wildcards) may be used in the character-pattern:

_ stands for any single character

% stands for any sequence of zero or more characters.

Note: Wildcard characters are only used as such in LIKE predicates. In any other context, the characters _ and % have their exact values.

The optional escape character is used to allow matching of the special characters _ and %. When the escape character prefixes _ and %, they are interpreted without any special meaning.

The character-value must be a string expression of length 1. To search for the escape character itself it must appear twice in immediate succession.

An escape character used in a pattern string may only be followed by another escape character or one of the wildcard characters, unless it is itself escaped (i.e. preceded by an escape character).

Examples:

LIKE predicate
Matches
LIKE '%A%'
any string containing an uppercase A
LIKE '%A\%\\' ESCAPE '\'
any string ending with A%\
LIKE '_ABC'
any 4-character string ending in ABC

A LIKE predicate where the pattern string does not contain any wildcard characters is essentially equivalent to a basic predicate using the "=" operator.

The comparison strings in the LIKE predicate are not conceptually padded with blanks, in contrast to the basic comparison.

Thus:

'SKYLINE ' = 'SKYLINE' is true

'SKYLINE ' LIKE 'SKYLINE ' is true

'SKYLINE ' LIKE 'SKYLINE%' is true

but

'SKYLINE ' LIKE 'SKYLINE' is false



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