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=",#{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>

（编辑：李大同）

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