where-if

<select id="listBySearch" resultType="java.lang.Integer">
        SELECT id FROM hospital 
        <where>
	        <if test="search.province!=null and search.province!=''">
	             province=#{search.province}
	        </if>
	        <if test="search.city!=null and search.city!=''">
	            AND city=#{search.city}
	        </if>
        </where>
    </select>
 

test裡面是條件 多個條件用and連線,if外加where標籤後如果第一個if不符合條件，第二個if會自動去掉開頭的 AND （不會去掉結尾的AND）SQL:

SELECT id FROM hospital  WHERE city='xxx'

set-if

 <update id="updateHospitalById">
        UPDATE user
		 <set >
		      <if test="name != null" >
		        name = #{name},
		      </if>
		      <if test="sex != null" >
		        sex = #{sex},
		      </if>
		</set>
        WHERE type = #{type}
    </update>
 

test裡面是條件 多個條件用and連線,if外加set標籤後編譯出來的sql會去掉sex = #{sex},中的,，如果條件都滿足則SQL為：

UPDATE user SET name='xxx' ,sex='xxx' WHERE type='xxx'

for

<select id="listByIds" resultType="hospital">
        SELECT * FROM hospital  
        <foreach collection="list" item="item" index="index" open="WHERE id IN (" separator="," close=")">
            #{item.id}
        </foreach>
    </select>
 

collection:要迴圈的集合
item：當前迭代物件
index：當前迭代次數
open：以什麼字元開始
separator：分割符
close：以什麼結束

如果list 的size為4，id分別為 1，2，3，4則SQL為：

SELECT * FROM hospital WHERE id IN(1,2,3,4)