[jeeplus] 使用笔记 (gridSelect、datetimepicker etc.)
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PeterChu •作者
MySql 中根据 判断某个字段(字符串)的长度后 按不同情况更新 同一个字段的值 的方法:
UPDATE m_levelformajor SET type = ( CASE WHEN 1 < LENGTH(number) AND LENGTH(number) < 3 THEN "2" WHEN 3 < LENGTH(number) AND LENGTH(number) < 5 THEN "3" WHEN 6 <= LENGTH(number) THEN "4" WHEN number IS NULL THEN "1" ELSE "1" END ) UPDATE m_levelformajor SET type = ( CASE WHEN number IS NULL THEN "1" ELSE "1" END ) SELECT id,name, number, type, parent_id,parent_ids , LENGTH(number) FROM m_levelformajor SELECT id,name, number, type, parent_id,parent_ids , LENGTH(number) FROM m_levelformajor WHERE LENGTH(number) <5 AND LENGTH(number) > 3 SELECT id,name, number, type, parent_id,parent_ids , LENGTH(number) FROM m_levelformajor WHERE 1 < LENGTH(number) AND LENGTH(number) <3 SELECT id,name, number, type, parent_id,parent_ids , LENGTH(number) FROM m_levelformajor WHERE LENGTH(number) <1```
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PeterChu •作者
SSM 中 MyBatis 的某个 xxxMapper.xml 中,是否可以这样写?
<if test="planMajorName != null and planMajorName != '' and r1 = '0'"> AND a.planmajorname = #{planMajorName} </if> <if test="planMajorName != null and planMajorName != '' and (r1 = null or r1 = '')"> AND a.planmajorname LIKE <if test="dbName == 'oracle'">'%'||#{planMajorName}||'%'</if> <if test="dbName == 'mssql'">'%'+#{planMajorName}+'%'</if> <if test="dbName == 'mysql'">concat('%',#{planMajorName},'%')</if> </if>
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PeterChu •作者
慎用
select *
当自己手写一些 sql 时,如果查找的对象/表中有封装了其他对象,那么,当 sql 中有
select *
时会导致封装对象为 Null 的现象。
因此,如果有会使用到封装的对象,那么 xml 中的 sql 还是加上映射关系吧。
eg:<!-- 根据年份、省份、高校、文理科、批次查找记录 findListByYPNWB --> <select id="findListByYPNWB" resultType="Eucode" > SELECT <include refid="EucodeColumns"/> FROM e_uecode a <include refid="EucodeJoins"/> WHERE a.year = #{year} AND a.province = #{province.id} AND a.universityid = #{university.id} AND a.wltype = #{wltype} AND a.schoolbatches = #{schoolBatches} AND (a.r3 != "2" OR ISNULL(a.r3)) AND (a.r3 != "3" OR ISNULL(a.r3)) </select>
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