The XDB Server supports the DB2 implementation of the LIKE string pattern matching operator. The syntax for a LIKE pattern match predicate appears below:
expression [NOT] LIKE
{special-register | host-variable | string-constant}
[ESCAPE {host-variable | string-constant}]
where:
| expression | The expression parameter string value is compared to the pattern string, and can be any valid expression-- as long as the result of the expression is a string. The expression can consist of a single table column name or contain a column name as part of the expression. |
| special-register | Indicates that the string is stored in the named special register. |
| host-variable | Indicates that the string is in the named host variable. The host variable must be already be defined in accordance with the rules for declaring string host variables. |
| string-constant | Includes the pattern as a string constant within the predicate. |
In each case, the pattern string value represented by either the special-register, host-variable or string-constant parameter is matched against the string value of expression -- for each table record specified by the query.
Pattern Strings
The host-variable and string-constant parameters can utilize two special reserved characters (wild card characters) -- the percent sign ( % ) and the underscore ( _ ) to perform pattern match searches against the string values in expression. The percent sign character matches any string (of any length), while the underscore character matches any single string character.
| ESCAPE |
The optional ESCAPE clause designates a special escape character, which if placed immediately before a percent ( % ) or underline ( _ ) character causes that percent or underline character to be literally interpreted as part of the pattern string. The escape character value can be specified with either a string-constant (enclosed in quotes) or host-variable (must not be a structure).