1.首先在oracle中的replace function窗口中添加方法

CREATE OR REPLACE FUNCTION LONG_TO_CHAR(IN_WHERE VARCHAR,
IN_TABLE_NAME VARCHAR,
IN_COLUMN VARCHAR2)
RETURN VARCHAR2 AS
V_RET VARCHAR2(32767);
V_SQL VARCHAR2(2000);

BEGIN
V_SQL := 'select ' || UPPER(IN_COLUMN) || ' from
' || UPPER(IN_TABLE_NAME) || ' where ' || IN_WHERE;
EXECUTE IMMEDIATE V_SQL
INTO V_RET;

RETURN V_RET;

END;

2.比如在视图中使用