Like predicate
The like predicate is used to test if a value matches a pattern.
Syntax
<like predicate> ::=
<match value> ( NOT )? LIKE <pattern value>
( ESCAPE <escape character> )?.
<match value> ::= <column reference>.
<pattern value> ::=
<string literal>
| <dynamic parameter specification>.
<escape character> ::=
<string literal>
| <dynamic parameter specification>.
The data types of the <match value> , <pattern value> and <escape character> must be character types and comparable to each other.
If an <escape character> is specified the length of its value must be one character.
The <like predicate> "match NOT LIKE pattern ESCAPE escape" is equivalent to the <boolean factor> "NOT ( match LIKE pattern ESCAPE escape )".
The <like predicate> "match NOT LIKE pattern" is equivalent to the <boolean factor> "NOT ( match LIKE pattern )".
If either the <match value> or the <pattern value> is the NULL value, the result of the <like predicate> is unknown.
If an <escape character> is specified and the <escape character> is the NULL value, the result of the <like predicate> is unknown.
The result of the <like predicate> is true, if the <match value> matches the <pattern value> , otherwise the result of the <like predicate> is false.
Matching is done by comparing character wise the <match value> with the <pattern value> where the underscore character '_' stands for exactly one arbitrary character and the percent character '%' stands for an arbitrary string (sequence of arbitrary length (including zero length) of arbitrary characters).
If an <escape character> is specified, the <escape character> can be used to escape the special meaning of the underscore and the percent character. Shall E be the <escape character> . Then the character sequence "E_" in the <pattern value> matches the occurrence of one underscore character "_" in the <match value> , the sequence "E%" in the <pattern value> matches the occurrence of one percent character "%" in the <match value> and the sequence "EE" in the <pattern value> matches the occurrence of one "E" in the <match value> , all other sequences that start with "E" are invalid.
Example
SELECT * FROM a WHERE c LIKE 'x%'
LIKE . This SELECT yields all rows from table a where the value of the column a.c starts with the character 'x'.