关于Mybatis动态sql中test的坑点总结

<if test="count == 1">
    AND ISNULL(t.count)
</if>

test="count == 1"
//当少打了一个等号
test="count = 1"//很不幸，这mybatis擅作主张的处理为返回了count，true、false将会由count决定

test="1 == count"
//当少打了一个等号
test="1 = count" //执行时，mybatis会很友好的给你抛个异常

<if test="type== 'AI' ">
    AND t.type = 1
</if>

<select id="findActiveBlogWithTitleLike" 
     parameterType="Blog" resultType="Blog">
  SELECT * FROM BLOG 
  WHERE state = ‘ACTIVE' 
  <if test="title != null">
    AND title like #{title}
  </if>
</select>

<select id="findActiveBlogWithTitleLike" 
     parameterType="Blog" resultType="Blog">
  SELECT * FROM BLOG 
  WHERE
  <if test="userId != null">
     state = ‘ACTIVE' 
  </if>

  <if test="title != null">
    AND title like #{title}
  </if>
</select>

SELECT * FROM BLOG 
  WHERE

<select id="findActiveBlogWithTitleLike" 
     parameterType="Blog" resultType="Blog">
  SELECT * FROM BLOG 
 <where>
  <if test="userId != null">
     state = ‘ACTIVE' 
  </if>

  <if test="title != null">
    AND title like #{title}
  </if>
 </where>
</select>

 SELECT * FROM BLOG 
     WHERE
    AND title like #{title}