comparing strings while executing a select statement

hi,

i need to compare select the rows from table dd02t into the internal table li_tabdef where dd02-ddtext contains the string s_string(taken as a parameter)

i can't write the where clause as

*where dd02t-ddlanguage CS s_string* since CS is not a valid comparison operator. i need to compare the value of sy-fdpos.

can you please help me with the select statement