mybatis动态sql中的trim标签的使用
<select id="findActiveBlogLike"
resultType="Blog">
SELECT * FROM BLOG
<trim prefix="WHERE" prefixoverride="AND|OR">
<if test="state != null">
AND state = #{state}
</if>
<if test="title != null">
AND title like #{title}
</if>
<if test="author != null and author.name != null">
AND author_name like #{author.name}
</if>
</trim>
</select>
都不为null的话sql语句为:SELECT * FROM BLOG where AND state= 'xx' and title like 'xx' AND author_name like 'xx' 在红色删除线的第一个AND是不存在的,上面两个属性的意思如下:
prefix :前缀
prefixOverrides :去掉第一个AND或者是OR
<update id="updateAuthorIfNecessary">
update Author
<trim prefix="SET" suffixOverrides="," suffix=" where id = #{id} ">
<if test="username != null">username=#{username},</if>
<if test="password != null">password=#{password},</if>
<if test="email != null">email=#{email},</if>
<if test="bio != null">bio=#{bio},</if>
</trim>
</update>
都不为null的话sql语句为:update Author SET username = 'xx',password='xx',email='xx',bio='xx' , where id = 'xx' 在红色删除线是不存在逗号的,而且自动加了一个SET前缀和WHERE后缀,上面三个属性的意义如下:
prefix :前缀
suffixoverride :去掉最后一个逗号(也可以是其他的标记,就像是上面前缀中的AND一样)
suffix :后缀