说明：

ew是mapper方法里的@Param(Constants.WRAPPER) Wrapper queryWrapper对象

1、${ew.customSqlSegment} 会直接在前面添加 where

@Select(select * from sys_user ${ew.customSqlSegment}）
List<SysUser> listPage(@Param(Constants.WRAPPER)  QueryWrapper queryWrapper)

2、${ew.sqlSegment} 就只有条件语句

 @Select(select * from sys_user  where ${ew.sqlSegment}）
 List<SysUser> listPage@Param(Constants.WRAPPER) QueryWrapper queryWrapper)

3、${ew.sqlSelect} 就是 queryWrapper.select(****) 你所定义需要查询的字段

实例1：

@Select(select ${ew.sqlSelect} from sys_user  ）
List<SysUser> listPage(@Param(Constants.WRAPPER) QueryWrapper queryWrapper)

实例2：

<select id="selectUser" resultType="com.example.demo.entity.User">
        select
            <if test="ew != null and ew.sqlSelect != null and ew.sqlSelect != ''">
                ${ew.sqlSelect}
            </if>
        from
            sys_user
        where is_deleted != 1
        <if test="ew != null">
            <if test="ew.nonEmptyOfWhere">
                AND
            </if>
            ${ew.sqlSegment}
        </if>
    </select>

4、${ew.sqlSet}用于update语句

boolean updateById(@Param("tableName") String tableName,@Param(Constants.WRAPPER) Wrapper wrapper);

实例1

<update id="updateById">
    update ${tableName} set ${ew.sqlSet} ${ew.customSqlSegment};
</update>

实例2

<update id="updateUser">
		update sys_user
		set ${ew.sqlSet}
		where ${ew.sqlSegment}
    </update>