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mybatis：updatebyexample与updateByExampleSelective

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07/26
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MyBatis，通常逆向工程工具生成接口和xml映射文件用于简单的单表操作。

有两个方法： updateByExample 和 updateByExampleSelective  ，作用是对数据库进行更新操作。（insert和insertSelective也一球样！）

注意：1，区别在于后者比前者多了动态标签<if test="xxx != null">的判断，有空值，不进行插入操作。

2，updateByExampleSelective可以不按主键更新，条件中可以不包含主键；updateByExample条件中必须包含主键。

updateByExample：

<update id="updateByExample" parameterType="map" >
update tb_item
set id = #{record.id,jdbcType=BIGINT},
title = #{record.title,jdbcType=VARCHAR},
sell_point = #{record.sellPoint,jdbcType=VARCHAR},
price = #{record.price,jdbcType=BIGINT},
num = #{record.num,jdbcType=INTEGER},
barcode = #{record.barcode,jdbcType=VARCHAR},
image = #{record.image,jdbcType=VARCHAR},
cid = #{record.cid,jdbcType=BIGINT},
status = #{record.status,jdbcType=TINYINT},
created = #{record.created,jdbcType=TIMESTAMP},
updated = #{record.updated,jdbcType=TIMESTAMP}
<if test="_parameter != null" >
<include refid="Update_By_Example_Where_Clause" />
</if>
</update>

updateByExampleSelective：

<update id="updateByExampleSelective" parameterType="map" >
update tb_item
<set >
<if test="record.id != null" >
id = #{record.id,jdbcType=BIGINT},
</if>
<if test="record.title != null" >
title = #{record.title,jdbcType=VARCHAR},
</if>
<if test="record.sellPoint != null" >
sell_point = #{record.sellPoint,jdbcType=VARCHAR},
</if>
<if test="record.price != null" >
price = #{record.price,jdbcType=BIGINT},
</if>
<if test="record.num != null" >
num = #{record.num,jdbcType=INTEGER},
</if>
<if test="record.barcode != null" >
barcode = #{record.barcode,jdbcType=VARCHAR},
</if>
<if test="record.image != null" >
image = #{record.image,jdbcType=VARCHAR},
</if>
<if test="record.cid != null" >
cid = #{record.cid,jdbcType=BIGINT},
</if>
<if test="record.status != null" >
status = #{record.status,jdbcType=TINYINT},
</if>
<if test="record.created != null" >
created = #{record.created,jdbcType=TIMESTAMP},
</if>
<if test="record.updated != null" >
updated = #{record.updated,jdbcType=TIMESTAMP},
</if>
</set>
<if test="_parameter != null" >
<include refid="Update_By_Example_Where_Clause" />
</if>
</update>

UpdateByExampleSelectivce使用：

ProLogExample example = new ProLogExample();
example.createCriteria().andNameEqualTo(xiaoming.getName());
proLogMapper.updateByExampleSelective(xiaoming, example);