oracle日期时间范围查询

字段为：字符串类型（char），长度为:10

SELECT * FROM testdatetime t WHERE 1=1 AND t.createdate >= 2011-06-01 AND t.createdate <= 2011-07-05;

SELECT * FROM testdatetime t WHERE 1=1 AND to_date(t.createdate,yyyy-MM-dd) 
between to_date(2011-06-01,yyyy-MM-dd) and to_date(20110705,yyyymmdd) ; 

字段为：字符串类型（char），长度为:20

SELECT * FROM testdatetime t WHERE 1=1 AND t.usedate >= 2011-06-01 AND t.usedate <= 2011-07-05;  
  
SELECT * FROM testdatetime t WHERE 1=1 AND to_date(t.usedate,yyyy-MM-dd HH24:MI:SS)
between to_date(2011-07-01 12:00:00,yyyy-MM-dd HH24:MI:SS) and to_date(20110702 12:00:00,yyyymmdd HH24:MI:SS) ;

字段为：日期时间类型（date）

SELECT * FROM testdatetime t WHERE 1=1 AND t.startdate >= to_date(2011-07-01,yyyy-MM-dd) AND t.startdate <= to_date(2011-07-02,yyyy-MM-dd);  
SELECT * FROM testdatetime t WHERE 1=1 AND t.startdate between to_date(2011-07-01,yyyy-MM-dd) AND to_date(2011-07-02,yyyy-MM-dd); 
SELECT * FROM testdatetime t WHERE 1=1 AND t.startdate = to_date(2011-07-01 12:00:00,yyyy-MM-dd HH24:MI:SS); 
SELECT * FROM testdatetime t WHERE 1=1 AND to_char(t.startdate,yyyy-MM-dd) = 2011-07-01;
SELECT * FROM testdatetime t WHERE 1=1 AND to_char(t.startdate,yyyy-MM-dd) >= 2011-07-01 AND to_char(t.startdate,yyyy-MM-dd) <= 2011-07-02;