Mybatis在注解上如何实现动态SQL

织梦狗教程 Java开发

2023-01-02

这篇文章主要介绍了Mybatis在注解上如何实现动态SQL，具有很好的参考价值，希望对大家有所帮助。如有错误或未考虑完全的地方，望不吝赐教

在注解上实现动态SQL

使用Mybatis注解实现sql语句，但是有些时候有些字段是空的，这时候这个空的字段就要从条件查询语句中删除，这个时候就需要用到动态Sql。

注解的动态语句支持以下

trim
where
set
foreach
if
choose
when
otherwise
bind

@Select({"<script> " +
        "select * from t_user " +
        "where  1=1 " +
        "<if test='userId!=null'> and id = #{userId}</if> " +
        "</script>"})

要加上标签就可以实现条件判断

但是在无法使用大于号、小于号，那如何解决这问题呢，其实只要把大于号、小于号转义即可

注解方式动态sql写法和注意事项

@Select({"<script>" +
            "select * from tb_examine" +
            "<where> 1 = 1" +
            "<if test = \" employeeId != null and  employeeId != '' \"> AND employee_id = #{employeeId} </if>" +
            "<if test = \" gradeId != null and gradeId != '' \"> AND grade_id = #{gradeId} </if>" +
            "<if test = \" year != null and year != '' \"> AND year like #{year} </if>" +
            "<if test = \" (statrMonth != null and statrMonth != '') and (endMonth == null or endMonth == '') \"> AND month &gt;= #{statrMonth} </if>" +
            "<if test = \" (statrMonth == null or  statrMonth == '') and (endMonth != null and endMonth != '')   \"> AND month &lt;= #{endMonth} </if>" +
            "<if test = \" (statrMonth != null and statrMonth != '') and (endMonth != null and endMonth != '')   \">AND month &gt;= #{statrMonth} AND month &lt;= #{endMonth}  </if>" +
            "</where>" +
            "</script>"})
public List<Examine> getName(Examine examine);