Question

mybatis 为什么没有智能忽略and

<if test="dateStart != null and dateStart != ''">
AND cDate >= concat(#{dateStart},' 00:00:00')
</if>
<if test="dateEnd != null and dateEnd != ''">
<![CDATA[
AND cDate <= concat(#{dateEnd},' 23:59:59')
]]>
</if>
如果第一个条件为空的话 执行的sql语句 select * from table where AND cDate <= concat(#{dateEnd},' 23:59:59')
为什么没有把and 忽略掉呢
<where>
...
<if test="dateStart != null and dateStart != ''">
AND cDate >= concat(#{dateStart},' 00:00:00')
</if>
<if test="dateEnd != null and dateEnd != ''">
<![CDATA[
AND cDate <= concat(#{dateEnd},' 23:59:59')
]]>
</if>

</where>
如果最后一个查询条件不为空，之前的都为空，and 就忽略不掉，sql语句就会select * from table where and cDate <= 2014-01-01 23:59;59

Answer 1

where 1=1
1=1 恒成立
统一后面的动态条件格式
and column1 = 122
and column2 = 222
and column3 = 333

Answer 2

WHERE 1=1

后面根据需要的条件，再添加条件