多表查询

1.双表查询

<select id="findAll" resultType="plan">
        select * from plan join dept on plan.dept_id=dept.id
        <where>
            <if test="null!=name and name!=''">
                and plan.name like concat('%',#{name},'%')
            </if>
        </where>
    </select>
    <resultMap type="Plan" id="plan">
        <id column="id" property="id"/>
        <result column="name" property="name"/>
        <result column="amount" property="amount"/>
        <result column="manager" property="manager"/>
        <result column="content" property="content"/>
        <association property="dept" javaType="Dept">
            <id column="id" property="id"/>
            <result column="name" property="name"/>
        </association>
    </resultMap>

2.三表查询

<resultMap type="com.liujin.cms.domain.Students" id="students">
        <id column="id" property="id"/>
        <result column="name" property="name"/>
        <result column="date" property="date"/>
        <collection property="types" ofType="com.liujin.cms.domain.Types">
            <id column="x_id" property="x_id"/>
            <result column="type" property="type"/>
        </collection>
    </resultMap>
    <select id="findAll" resultMap="students">
        select s.id id,s.name name,s.date date,t.x_id x_id,t.type type from students s join
        s_t on s.id=s_t.id join types t on s_t.x_id=t.x_id
        <where>
            <if test="null!=name and name!=''">
                and name like concat('%',#{name},'%')
            </if>
            <if test="null!=x_id and x_id">
                and x_id=#{x_id}
            </if>
        </where>
    </select>

大于小于号

<if test="null!=date1 and date1!=''">
                and date &gt;=#{date1}
            </if>
            <if test="null!=date2 and date2!=''">
                and date &lt;=#{date2}
            </if>