string_function 
<
string_function> ::=
<string_spec> || <string_spec>
| <string_spec> & <string_spec>
| SUBSTR ( <string_spec>, <expression>[, <expression>] )
| LFILL ( <string_spec>, <string_literal> [,<unsigned_integer> ] )
| RFILL ( <string_spec>, <string_literal> [,<unsigned_integer> ] )
| LPAD ( <string_spec>, <expression>, <string_literal> [,<unsigned_integer> ] )
| RPAD ( <string_spec>, <expression>, <string_literal> [,<unsigned_integer> ] )
| TRIM ( <string_spec>[, <string_spec> ] )
| LTRIM ( <string_spec>[, <string_spec> ] )
| RTRIM ( <string_spec>[, <string_spec> ] )
| EXPAND ( <string_spec>, <unsigned_integer> )
| UPPER ( <string_spec> )
| LOWER ( <string_spec> )
| INITCAP ( <string_spec> )
| REPLACE ( <string_spec>, <string_spec>[, <string_spec> ] )
| TRANSLATE ( <string_spec>, <string_spec>, <string_spec> )
| MAPCHAR ( <string_spec>[, <unsigned_integer> ] [, <mapchar_set_name> ] )
| ALPHA ( <string_spec>[, <unsigned_integer> ] )
| ASCII ( <string_spec> )
| EBCDIC ( <string_spec> )
| SOUNDEX ( <string_spec> )