动态SQL
2021/9/9 19:07:07
本文主要是介绍动态SQL,对大家解决编程问题具有一定的参考价值,需要的程序猿们随着小编来一起学习吧!
if choose (when, otherwise) trim (where, set) foreach
if
<select id="findActiveBlogWithTitleLike" resultType="Blog"> SELECT * FROM BLOG WHERE 1=1 <if test="title != null"> AND title like #{title} </if> </select>
choose (when, otherwise)
<select id="findActiveBlogLike" resultType="Blog"> SELECT * FROM BLOG WHERE state = ‘ACTIVE’ <choose> <when test="title != null"> AND title like #{title} </when> <when test="author != null and author.name != null"> AND author_name like #{author.name} </when> <otherwise> AND featured = 1 </otherwise> </choose> </select>
trim、where、set
<select id="findActiveBlogLike" resultType="Blog"> SELECT * FROM BLOG <where> <if test="state != null"> state = #{state} </if> <if test="title != null"> AND title like #{title} </if> <if test="author != null and author.name != null"> AND author_name like #{author.name} </if> </where> </select>
<update id="updateAuthorIfNecessary"> update Author <set> <if test="username != null">username=#{username},</if> <if test="password != null">password=#{password},</if> <if test="email != null">email=#{email},</if> <if test="bio != null">bio=#{bio}</if> </set> where id=#{id} </update>
所谓的动态SQL,本质还是SQL语句,只是我们可以在SQL层面,去执行一个逻辑代码
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