今天调试毕设项目的时候，改了mapper的一些sql语句后，一直报这个错：

Mybatis报错Translating SQLException with SQL state '42000', error code '1064', message [You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'LEFT JOIN ah_activity aha ON aha.id = ahua.activity_id
  		LEFT JOIN ah_activity' at line 7]; SQL was [] for task [
### Error querying database.  Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'LEFT JOIN ah_activity aha ON aha.id = ahua.activity_id
  		LEFT JOIN ah_activity' at line 7
### The error may exist in crj/ah/ssm/mapper/custom/AhUserActivityMapperCustom.xml
### The error may involve crj.ah.ssm.mapper.custom.AhUserActivityMapperCustom.getCount-Inline
### The error occurred while setting parameters
### SQL: select          count(1)         FROM      ah_user_activity ahua            WHERE  ahua.user_id = 7      LEFT JOIN ah_activity aha ON aha.id = ahua.activity_id     LEFT JOIN ah_activity_space ahas ON ahas.id = ahua.space_id      LEFT JOIN ah_activity_area ahaa ON ahaa.id = ahua.area_id      LEFT JOIN ah_activity_seat ahase ON ahase.id = ahua.seat_id      LEFT JOIN ah_user ahu ON ahu.id = ahua.user_id      LEFT JOIN ah_manager ahm1 ON ahm1.id = ahua.createuser   LEFT JOIN ah_manager ahm2 ON ahm2.id = ahua.updateuser      order by ahua.updatetime desc
### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'LEFT JOIN ah_activity aha ON aha.id = ahua.activity_id
  		LEFT JOIN ah_activity' at line 7
]

检查了好多次，还是觉得语法没有错啊！！！！后来才发现，where 应该放在left join 语句的后面！!!!!

附上sql各语句的执行顺序

(8)SELECT (9)DISTINCT  (11)<Top Num> <select list>
(1)FROM [left_table]
(3)<join_type> JOIN <right_table>
(2)ON <join_condition>
(4)WHERE <where_condition>
(5)GROUP BY <group_by_list>
(6)WITH <CUBE | RollUP>
(7)HAVING <having_condition>
(10)ORDER BY <order_by_list>
逻辑查询处理阶段简介
FROM：对FROM子句中的前两个表执行笛卡尔积（Cartesian product)(交叉联接），生成虚拟表VT1
ON：对VT1应用ON筛选器。只有那些使<join_condition>为真的行才被插入VT2。
OUTER(JOIN)：如 果指定了OUTER JOIN（相对于CROSS JOIN 或(INNER JOIN),保留表（preserved table：左外部联接把左表标记为保留表，右外部联接把右表标记为保留表，完全外部联接把两个表都标记为保留表）中未找到匹配的行将作为外部行添加到 VT2,生成VT3.如果FROM子句包含两个以上的表，则对上一个联接生成的结果表和下一个表重复执行步骤1到步骤3，直到处理完所有的表为止。
WHERE：对VT3应用WHERE筛选器。只有使<where_condition>为true的行才被插入VT4.
GROUP BY：按GROUP BY子句中的列列表对VT4中的行分组，生成VT5.
CUBE|ROLLUP：把超组(Suppergroups)插入VT5,生成VT6.
HAVING：对VT6应用HAVING筛选器。只有使<having_condition>为true的组才会被插入VT7.
SELECT：处理SELECT列表，产生VT8.
DISTINCT：将重复的行从VT8中移除，产生VT9.
ORDER BY：将VT9中的行按ORDER BY 子句中的列列表排序，生成游标（VC10).
TOP：从VC10的开始处选择指定数量或比例的行，生成表VT11,并返回调用者。

其实，这种错通常都是sql语句写错，一定是！要细心检查啊！！！

如果你觉得语法没错，那可能你不小心用了保留字