MySQL :
SELECT * FROM tbl_name WHERE column_name LIKE "%$username$%"
ORACLE :
SELECT * FROM tbl_name WHERE column_name LIKE '%' || #username# || '%'
SYBASE/SQL SERVER
SELECT * FROM tbl_name WHERE column_name LIKE "%$username$%"
ORACLE :
SELECT * FROM tbl_name WHERE column_name LIKE '%' || #username# || '%'
SYBASE/SQL SERVER
SELECT * from tbl_name WHERE column_name LIKE '%' + #username# + '%'