錯誤的按日期分割槽例子
最直觀的方法，就是直接用年月日這種日期格式來進行常規的分割槽：
PLAIN TEXT
CODE:

mysql>  create table rms (d date)
    ->  partition by range (d)
    -> (partition p0 values less than ('1995-01-01'),
    ->  partition p1 VALUES LESS THAN ('2010-01-01'));

 
上面的例子中，就是直接用"Y-m-d"的格式來對一個table進行分割槽，可惜想當然往往不能奏效，會得到一個錯誤資訊:
ERROR 1064 (42000): VALUES value must be of same type as partition function near '),
partition p1 VALUES LESS THAN ('2010-01-01'))' at line 3
上述分割槽方式沒有成功，而且明顯的不經濟，老練的DBA會用整型數值來進行分割槽：
PLAIN TEXT
CODE:

mysql> CREATE TABLE part_date1
    ->      (  c1 int default NULL,
    ->  c2 varchar(30) default NULL,
    ->  c3 date default NULL) engine=myisam
    ->      partition by range (cast(date_format(c3,'%Y%m%d') as signed))
    -> (PARTITION p0 VALUES LESS THAN (19950101),
    -> PARTITION p1 VALUES LESS THAN (19960101) ,
    -> PARTITION p2 VALUES LESS THAN (19970101) ,
    -> PARTITION p3 VALUES LESS THAN (19980101) ,
    -> PARTITION p4 VALUES LESS THAN (19990101) ,
    -> PARTITION p5 VALUES LESS THAN (20000101) ,
    -> PARTITION p6 VALUES LESS THAN (20010101) ,
    -> PARTITION p7 VALUES LESS THAN (20020101) ,
    -> PARTITION p8 VALUES LESS THAN (20030101) ,
    -> PARTITION p9 VALUES LESS THAN (20040101) ,
    -> PARTITION p10 VALUES LESS THAN (20100101),
    -> PARTITION p11 VALUES LESS THAN MAXVALUE );
 

Query OK, 0 rows affected (0.01 sec)
 
搞定？接著往下分析
PLAIN TEXT
CODE:

mysql> explain partitions
    -> select count(*) from part_date1 where
    ->      c3> '1995-01-01' and c3 <'1995-12-31'\G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: part_date1
   partitions: p0,p1,p2,p3,p4,p5,p6,p7,p8,p9,p10,p11
         type: ALL
possible_keys: NULL
          key: NULL
      key_len: NULL
          ref: NULL
         rows: 8100000
        Extra: Using where
1 row in set (0.00 sec)
 

 
萬惡的mysql居然對上面的sql使用全表掃描，而不是按照我們的日期分割槽分塊查詢。原文中解釋到MYSQL的優化器並不認這種日期形式的分割槽，花了大量的篇幅來引誘俺走上歧路，過分。
正確的日期分割槽例子
mysql優化器支援以下兩種內建的日期函式進行分割槽：
TO_DAYS()
YEAR()
看個例子：
PLAIN TEXT
CODE:

mysql> CREATE TABLE part_date3
    ->      (  c1 int default NULL,
    ->  c2 varchar(30) default NULL,
    ->  c3 date default NULL) engine=myisam
    ->      partition by range (to_days(c3))
    -> (PARTITION p0 VALUES LESS THAN (to_days('1995-01-01')),
    -> PARTITION p1 VALUES LESS THAN (to_days('1996-01-01')) ,
    -> PARTITION p2 VALUES LESS THAN (to_days('1997-01-01')) ,
    -> PARTITION p3 VALUES LESS THAN (to_days('1998-01-01')) ,
    -> PARTITION p4 VALUES LESS THAN (to_days('1999-01-01')) ,
    -> PARTITION p5 VALUES LESS THAN (to_days('2000-01-01')) ,
    -> PARTITION p6 VALUES LESS THAN (to_days('2001-01-01')) ,
    -> PARTITION p7 VALUES LESS THAN (to_days('2002-01-01')) ,
    -> PARTITION p8 VALUES LESS THAN (to_days('2003-01-01')) ,
    -> PARTITION p9 VALUES LESS THAN (to_days('2004-01-01')) ,
    -> PARTITION p10 VALUES LESS THAN (to_days('2010-01-01')),
    -> PARTITION p11 VALUES LESS THAN MAXVALUE );
 

Query OK, 0 rows affected (0.00 sec)
 
以to_days()函式分割槽成功，我們分析一下看看：
PLAIN TEXT
CODE:

mysql> explain partitions
    -> select count(*) from part_date3 where
    ->      c3> date '1995-01-01' and c3 <date '1995-12-31'\G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: part_date3
   partitions: p1
         type: ALL
possible_keys: NULL
          key: NULL
      key_len: NULL
          ref: NULL
         rows: 808431
        Extra: Using where
1 row in set (0.00 sec)

 
可以看到，mysql優化器這次不負眾望，僅僅在p1分割槽進行查詢。在這種情況下查詢，真的能夠帶來提升查詢效率麼？下面分別對這次建立的part_date3和之前分割槽失敗的part_date1做一個查詢對比：
PLAIN TEXT
CODE:

mysql> select count(*) from part_date3 where
    ->      c3> date '1995-01-01' and c3 <date '1995-12-31';
+----------+
| count(*) |
+----------+
|   805114 |
+----------+
1 row in set (4.11 sec)
 
mysql> select count(*) from part_date1 where
    ->      c3> date '1995-01-01' and c3 <date '1995-12-31';
+----------+
| count(*) |
+----------+
|   805114 |
+----------+
1 row in set (40.33 sec)

 
可以看到，分割槽正確的話query花費時間為4秒，而分割槽錯誤則花費時間40秒（相當於沒有分割槽），效率有90％的提升！所以我們千萬要正確的使用分割槽功能，分割槽後務必用explain驗證，這樣才能獲得真正的效能提升。


注意：
在mysql5.1中建立分割槽表的語句中，只能包含下列函式：

ABS()
CEILING() and FLOOR() （在使用這2個函式的建立分割槽表的前提是使用函式的分割槽鍵是INT型別），例如
mysql> CREATE TABLE t (c FLOAT) PARTITION BY LIST( FLOOR(c) )( -> PARTITION p0 VALUES IN (1,3,5), -> PARTITION p1 VALUES IN (2,4,6) -> );; ERROR 1491 (HY000): The PARTITION function returns the wrong type   mysql> CREATE TABLE t (c int) PARTITION BY LIST( FLOOR(c) )( -> PARTITION p0 VALUES IN (1,3,5), -> PARTITION p1 VALUES IN (2,4,6) -> ); Query OK, 0 rows affected (0.01 sec)
DAY()
DAYOFMONTH()
DAYOFWEEK()
DAYOFYEAR()
DATEDIFF()
EXTRACT()
HOUR()
MICROSECOND()
MINUTE()
MOD()
MONTH()
QUARTER()
SECOND()
TIME_TO_SEC()
TO_DAYS()
WEEKDAY()
YEAR()
YEARWEEK()