trim标签中涉及到的属性
属性 | 描述 |
---|---|
prefix | 给SQL语句拼接的前缀 |
suffix | 给SQL语句拼接的后缀 |
prefixOverrides | 去除sql语句前面的关键字或字符,该关键字由prefixOverrides属性,指定,比如改属性指定为“AND“,那么当sql语句的开头为“AND”时候,trim标签将会去除该“AND” |
suffixOverrides | 去除sql语句后面的关键字或字符,该关键字由suffixOverrides 属性 |
<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>
</select>
使用where标签
where 元素只会在至少有一个子元素的条件返回 SQL 子句的情况下才去插入“WHERE”子句,。而且,若语句的开头为“AND”或“OR”,where 元素也会将它们去除。
<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>
使用trim标签
<trim prefix="WHERE" prefixOverrides="AND">
<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>
</trim>