对mybastis 的理解1--xml中的动态sql设计

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="org.xnat.BaseDao">
<!-- 新增v1(以v开头的是版本的意思)-->
<insert id="insert">
insert into ${tableName}
<foreach item="item" index="index" collection="list" open="(" separator="," close=")">
${item.key}
</foreach>
values
<foreach item="item" index="index" collection="list" open="(" separator="," close=")">
#{item.value}
</foreach>
</insert>
<!-- 新增v1_2
useGeneratedKeys="true" keyProperty="id"
-->
<insert id="insert_v1_2" parameterType="map">
insert into ${tableName}
<foreach item="item" index="index" collection="autoMaps" open="(" separator="," close=")">
${item.key}
</foreach>
values
<foreach item="item" index="index" collection="autoMaps" open="(" separator="," close=")">
#{item.value}
</foreach>
<selectKey resultType="int" keyProperty="autoKey" order="AFTER">
select LAST_INSERT_ID() as autoKey
</selectKey>
<!--
-->
</insert>

<!-- 查询select_v4-->
<select id="select_v4" resultType="hashmap">
select
<!-- 选择的字段 -->
<foreach collection="selectFields" item="item" separator=",">`${item}`</foreach>
from ${tableName}
<!-- 条件 -->
<where>
<if test="conditions != null">
<foreach collection="conditions" item="condition" separator=" and ">
<!--
${condition.key} ${condition.denotation} #{condition.value}
这种不能适应　denotation　为 "in" value 为 "(v1, v2)"
${condition.key} ${condition.denotation} ${condition.value}
这种不能适应　 ${condition.value}　为字符串
-->
`${condition.key}` ${condition.denotation} #{condition.value}
</foreach>
</if>
</where>
<!-- 分组 list<String>-->
<if test="group != null">
group by
<foreach collection="group" item="item" separator=", ">
${item}
</foreach>
</if>
<!-- group 后的having 条件 -->
<if test="havingSql != null and group != null">
${havingSql}
</if>
<!-- 排序 -->
<if test="sort != null">
order by
<foreach collection="sort" item="item" separator=", ">
${item.key} ${item.value}
</foreach>
</if>
<!-- 分页 -->
<if test="page != null">
LIMIT #{page.start}, #{page.limit}
</if>
</select>
<!-- 查询select_v4_2-->
<select id="select_v4_2" resultType="hashmap">
select
<!-- 选择的字段 -->
<foreach collection="selectFields" item="item" separator=",">`${item}`</foreach>
from ${tableName}
<!-- 条件 -->
<if test="conditionSql != null">
${conditionSql}
</if>
<!-- 分组 list<String>-->
<if test="group != null">
group by
<foreach collection="group" item="item" separator=", ">
${item}
</foreach>
</if>
<!-- group 后的having 条件 -->
<if test="havingSql != null and group != null">
${havingSql}
</if>
<!-- 排序 -->
<if test="sort != null">
order by
<foreach collection="sort" item="item" separator=", ">
${item.key} ${item.value}
</foreach>
</if>
<!-- 分页 -->
<if test="page != null">
LIMIT #{page.start}, #{page.limit}
</if>
</select>
<!-- 删除_v3-->
<delete id="delete_v3">
delete from ${tableName}
<where>
<if test="conditions != null">
<foreach item="item" index="index" collection="conditions" separator=" and ">
${item.key}${item.denotation}#{item.value}
</foreach>
</if>
</where>
</delete>
<!-- 删除_v3-->
<delete id="delete_v3_2">
delete from ${tableName}
<if test="conditionSql != null">${conditionSql}</if>
</delete>

<!-- 更新_v2-->
<update id="update_v2">
update ${tableName}
<set>
<foreach item="item" index="index" collection="list" separator=",">
${item.key}=#{item.value}
</foreach>
</set>
<where>
<if test="conditions != null">
<foreach item="item" index="index" collection="conditions" separator=" and ">
${item.key} ${item.denotation} #{item.value}
</foreach>
</if>
</where>
</update>
<!-- 更新_v2-->
<update id="update_v2_2">
update ${tableName}
<set>
<foreach item="item" index="index" collection="list" separator=",">
${item.key}=#{item.value}
</foreach>
</set>
<if test="conditionSql != null">${conditionSql}</if>
</update>

<!-- 查询实体存在的数量-->
<select id="getTotal" resultType="int">
select count(*) from ${tableName}
<where>
<if test="conditions != null">
<foreach item="item" index="index" collection="conditions" separator=" and ">
<!--
${item.key} ${item.denotation} #{item.value}
不能用于　key != ''
-->
`${item.key}` ${item.denotation} #{item.value}
</foreach>
</if>
</where>
</select>
<!-- 查询实体存在的数量-->
<select id="getTotal_v1_2" resultType="int">
select count(*) from ${tableName}
<if test="conditionSql != null">${conditionSql}</if>
</select>

<!-- 统计一个字段所有值的和-->
<select id="countField" resultType="long">
select sum(${fieldName}) from ${tableName}
<where>
<if test="conditions != null">
<foreach item="item" index="index" collection="conditions" separator=" and ">
`${item.key}` ${item.denotation} #{item.value}
</foreach>
</if>
</where>
</select>

<!-- 自定义sql查询-->
<select id="selectSql" resultType="hashmap">
${sql}
</select>

</mapper>