我就废话不多说了，大家还是直接看代码吧~
<!-- 查询物品的id -->
<select id="checkItemsId" parameterType="pd" resultType="java.lang.Integer">
SELECT
i.itemsid
FROM pq_goods_items i
<where>
<!--方式一使用choose的方式查询-->
<!-- <choose>
<when test="parentId !=0 ">parentTypeId=#{parentId}</when>
<when test="parentId==0">parentTypeId is null</when>
</choose> -->
<!--方式二使用if的方式查询-->
<if test="color!=null">
i.personone=#{personone}
AND i.persontwo=#{persontwo}
AND i.color=#{color}
</if>
<if test="color==null">
i.personone=#{personone}
AND i.persontwo=#{persontwo}
AND i.color is null
</if>
</where>
</select>
需要注意的是 使用了where标签以后，sql中不在使用where字段来限制条件
如果判断条件有多个 中间用 and 表示并列
<if test="color!=null and personone!=null">
补充：mybaits中if 多个test 和 if else 分支支持
mybaits中if 多个test
<select id="selectByDynamicallyWithPage" parameterType="map" resultMap="BaseResultMap">
select
<include refid="Base_Column_List" />
from gene_polymorphism
<where>
diag_id = #{conds.diagId,jdbcType=INTEGER}
<if test="conds.chromesome!=null and conds.chromesome!=''">
and chromesome = #{conds.chromesome,jdbcType=VARCHAR}
</if>
<if test="conds.startPos!=null">
and start_pos >= #{conds.startPos,jdbcType=BIGINT}
</if>
</where>
</select>
if else分支：
<select id="selectByDynamicallyWithPage" parameterType="map" resultMap="BaseResultMap">
select
<include refid="Base_Column_List" />
from gene_polymorphism
<where>
diag_id = #{conds.diagId,jdbcType=INTEGER}
<if test="conds.chromesome!=null">
and chromesome = #{conds.chromesome,jdbcType=VARCHAR}
</if>
<if test="conds.startPos!=null">
and start_pos >= #{conds.startPos,jdbcType=BIGINT}
</if>
<if test="conds.endPos!=null">
and end_pos <= #{conds.endPos,jdbcType=BIGINT}
</if>
<if test="conds.geneTypes!=null">
<!--and gene_type in-->
<!--<foreach collection="conds.geneTypes" open="(" close=")" item="item" separator="," >-->
<!--#{item,jdbcType=VARCHAR}-->
<!--</foreach>-->
and (
<foreach collection="conds.geneTypes" item="item" separator="or">
gene_type like CONCAT('%',CONCAT(#{item,jdbcType=VARCHAR}, '%'))
</foreach>
)
</if>
<if test="conds.geneChange!=null">
and gene_change like CONCAT('%',CONCAT(#{conds.geneChange,jdbcType=VARCHAR}, '%'))
</if>
</where>
order by
<trim suffixOverrides=",">
<choose>
<when test="conds.chromesomeSort!=null and conds.chromesomeSort=='asc'">
chromesome asc ,
</when>
<when test="conds.chromesomeSort!=null and conds.chromesomeSort=='desc'">
chromesome desc ,
</when>
</choose>
<choose>
<when test="conds.startPosSort!=null and conds.startPosSort=='asc'">
start_pos asc ,
</when>
<when test="conds.startPosSort!=null and conds.startPosSort=='desc'">
start_pos desc ,
</when>
<otherwise>
id desc
</otherwise>
</choose>
</trim>
limit #{startRow,jdbcType=INTEGER} ,#{pageSize,jdbcType=INTEGER}
<!-- order by id desc limit #{startRow,jdbcType=INTEGER} ,#{pageSize,jdbcType=INTEGER} -->
</select>
以上为个人经验，希望能给大家一个参考，也希望大家多多支持。如有错误或未考虑完全的地方，望不吝赐教。
