Mybatis--动态SQL(foreach,sql)

foreach标签：collection:当前要循环的数组或集合 item：数组中的每一个数据 separator：每一次循环体的分隔符 open|close：当前循环的内容以什么开始|结束

<delete id="deleteByIds">
        delete from tb_brand where id in
        <foreach collection="ids" item="id" separator="," open="(" close=")">
            #{id}
        </foreach>
</delete>

sql标签：将常用的SQL片段进行记录，需要用时可直接引入
设置SQL片段：<sql id="empcolumns">eid,emp_name, age,sex,email</sql>
引用SQL片段：<include refid="empcolumns"></include>

<sql id="empcolumns">eid,emp_name, age,sex,email</sql>

<select id="getEmpBycondition" resultType="Emp">
    select <include refid="empcolumns"></include> from t_emp
    <trim prefix="where" suffixoverrides="and |or">
        <if test="empName != null and empName !="">
            emp_name =#{ empName} and
        </if>
    </trim>
</select>