ibatis3 Dynamic SQL

1.sql 将常用sql抽取出来，在需要的地方includ

<sql id="bankColumns"> id,bankAccount,bankName</sql>

<select id="selectAll" resultMap="BankMap">
select
<include refid="bankColumns" />
from bank
</select>


2.if 用于判断
<select id="select" parameterType="Bank" resultMap="BankMap">
  select
  <include refid="bankColumns" />
  from bank
  <trim prefix="WHERE" prefixOverrides="AND |OR ">
   <if test="bankName != null"> bankName = #{bankName}</if>
   <if test="bankAccount != null">and bankAccount = #{bankAccount}</if>
  </trim>
  <!--
   <where> <choose> <when test="bankName != null"> and bankName =
   #{bankName} </when> <when test="bankAccount != null"> and bankAccount
   = #{bankAccount} </when> <otherwise> and 1=1 </otherwise> </choose>
   </where>
  -->
</select>

3.choose用于选择
<select id="select" parameterType="Bank" resultMap="BankMap">
  select
  <include refid="bankColumns" />
  from bank
  <where>
   <choose>
   <when test="bankName != null">
   and bankName = #{bankName}
   </when>
   <when test="bankAccount != null"> and bankAccount
   = #{bankAccount} </when>
   <otherwise> and 1=1 </otherwise>
   </choose>
  </where>
</select>

4.foreach用于遍历循环
<select id="selectBank" resultMap="BankMap" parameterType="list"
  useCache="true" flushCache="false">
  select
  <include refid="bankColumns" />
  from bank where id in

  <foreach index="index" item="item" collection="list" open="("
   separator="," close=")">
   #{item}
      </foreach>
</select>

note:
数组类型，在配置文件用数组的组成类型。
如果传入的参数是数组, 系统会自动将参数包装成map,name为“array”
如果传入的参数是list,系统会自动将参数包装成map,name为“list”
如果传入的参数是map, 系统会自动将参数包装成map,name为“list”
作为collection的参数


5.set 用于更新
<update id="update" parameterType="Bank">
  update bank
  <set>
   <if test="bankName != null"> bankName = #{bankName},</if>
   <if test="bankAccount != null"> bankAccount = #{bankAccount},</if>
  </set>
  where id=#{id}
</update>

note：where,set动态产生sql关键字，
where 会去掉where 后面的and 和or.
set 会去掉set后面的,号