简述Mybatis的动态SQL是什么意思
- Mybatis提供的动态SQL不同于传统的SQL拼接，可有效防止语句错误。
- Mybatis实现动态SQL的元素有
if、choose、when、otherwise、trim、where、set、foreach
代码示例：
<select id="foo" parameterType="Blog" resultType="Blog">
select * from t_blog where 1 = 1
<if test="title != null">
and title = #{title}
</if>
<if test="content != null">
and content = #{content}
</if>
<if test="owner != null">
and owner = #{owner}
</if>
</select>
<select id="foo" parameterType="Blog" resultType="Blog">
select * from t_blog where 1 = 1
<choose>
<when test="title != null">
and title = #{title}
</when>
<when test="content != null">
and content = #{content}
</when>
<otherwise>
and owner = "owner1"
</otherwise>
</choose>
</select>
<select id="bar" resultType="Blog">
select * from t_blog where id in
<foreach collection="array" index="index"
item="item" open="(" separator="," close=")">
#{item}
</foreach>
</select>
