iBatis习惯用的16条SQL语句_Java教程-查字典教程网

摘要：iBatis简介：iBatis是apache的一个开源项目，一个O/RMapping解决方案，iBatis最大的特点就是小巧，上手很快。如果...

iBatis 简介：

iBatis 是apache 的一个开源项目，一个O/R Mapping 解决方案，iBatis 最大的特点就是小巧，上手很快。如果不需要太多复杂的功能，iBatis 是能够满足你的要求又足够灵活的最简单的解决方案，现在的iBatis 已经改名为Mybatis 了。

官网为：http://www.mybatis.org/

1.输入参数为单个值

<delete id="com.fashionfree.stat.accesslog.deleteMemberAccessLogsBefore" parameterClass="long"> delete from MemberAccessLog where accessTimestamp = #value# </delete> <delete id="com.fashionfree.stat.accesslog.deleteMemberAccessLogsBefore" parameterClass="long"> delete from MemberAccessLog where accessTimestamp = #value# </delete>

2.输入参数为一个对象

<insert id="com.fashionfree.stat.accesslog.MemberAccessLog.insert" parameterClass="com.fashionfree.stat.accesslog.model.MemberAccessLog> insert into MemberAccessLog ( accessLogId, memberId, clientIP, httpMethod, actionId, requestURL, accessTimestamp, extend1, extend2, extend3 ) values ( #accessLogId#, #memberId#, #clientIP#, #httpMethod#, #actionId#, #requestURL#, #accessTimestamp#, #extend1#, #extend2#, #extend3# ) </insert> <insert id="com.fashionfree.stat.accesslog.MemberAccessLog.insert" parameterClass="com.fashionfree.stat.accesslog.model.MemberAccessLog> insert into MemberAccessLog ( accessLogId, memberId, clientIP, httpMethod, actionId, requestURL, accessTimestamp, extend1, extend2, extend3 ) values ( #accessLogId#, #memberId#, #clientIP#, #httpMethod#, #actionId#, #requestURL#, #accessTimestamp#, #extend1#, #extend2#, #extend3# ) </insert>

3.输入参数为一个java.util.HashMap

<select id="com.fashionfree.stat.accesslog.selectActionIdAndActionNumber" parameterClass="hashMap" resultMap="getActionIdAndActionNumber"> select actionId, count(*) as count from MemberAccessLog where memberId = #memberId# and accessTimestamp > #start# and accessTimestamp <= #end# group by actionId </select> <select id="com.fashionfree.stat.accesslog.selectActionIdAndActionNumber" parameterClass="hashMap" resultMap="getActionIdAndActionNumber"> select actionId, count(*) as count from MemberAccessLog where memberId = #memberId# and accessTimestamp > #start# and accessTimestamp <= #end# group by actionId </select>

4.输入参数中含有数组

<insert id="updateStatusBatch" parameterClass="hashMap"> update Question set status = #status# <dynamic prepend="where questionId in"> <isNotNull property="actionIds"> <iterate property="actionIds" open="(" close=")" conjunction=","> #actionIds[]# </iterate> </isNotNull> </dynamic> </insert> <insert id="updateStatusBatch" parameterClass="hashMap"> update Question set status = #status# <dynamic prepend="where questionId in"> <isNotNull property="actionIds"> <iterate property="actionIds" open="(" close=")" conjunction=","> #actionIds[]# </iterate> </isNotNull> </dynamic> </insert>

说明：actionIds为传入的数组的名字；使用dynamic标签避免数组为空时导致sql语句语法出错；使用isNotNull标签避免数组为null时ibatis解析出错

5.传递参数只含有一个数组

<select id="com.fashionfree.stat.accesslog.model.StatMemberAction.selectActionIdsOfModule" resultClass="hashMap"> select moduleId, actionId from StatMemberAction <dynamic prepend="where moduleId in"> <iterate open="(" close=")" conjunction=","> #[]# </iterate> </dynamic> order by moduleId </select> <select id="com.fashionfree.stat.accesslog.model.StatMemberAction.selectActionIdsOfModule" resultClass="hashMap"> select moduleId, actionId from StatMemberAction <dynamic prepend="where moduleId in"> <iterate open="(" close=")" conjunction=","> #[]# </iterate> </dynamic> order by moduleId </select>

说明：注意select的标签中没有parameterClass一项

另：这里也可以把数组放进一个hashMap中，但增加额外开销，不建议使用

6.让ibatis把参数直接解析成字符串

<select id="com.fashionfree.stat.accesslog.selectSumDistinctCountOfAccessMemberNum" parameterClass="hashMap" resultClass="int"> select count(distinct memberId) from MemberAccessLog where accessTimestamp >= #start# and accessTimestamp < #end# and actionId in $actionIdString$ </select> <select id="com.fashionfree.stat.accesslog.selectSumDistinctCountOfAccessMemberNum" parameterClass="hashMap" resultClass="int"> select count(distinct memberId) from MemberAccessLog where accessTimestamp >= #start# and accessTimestamp < #end# and actionId in $actionIdString$ </select>

说明：使用这种方法存在sql注入的风险，不推荐使用

7.分页查询 (pagedQuery)

<select id="com.fashionfree.stat.accesslog.selectMemberAccessLogBy" parameterClass="hashMap" resultMap="MemberAccessLogMap"> <include refid="selectAllSql"/> <include refid="whereSql"/> <include refid="pageSql"/> </select> <select id="com.fashionfree.stat.accesslog.selectMemberAccessLogBy.Count" parameterClass="hashMap" resultClass="int"> <include refid="countSql"/> <include refid="whereSql"/> </select> <sql id="selectAllSql"> select accessLogId, memberId, clientIP, httpMethod, actionId, requestURL, accessTimestamp, extend1, extend2, extend3 from MemberAccessLog </sql> <sql id="whereSql"> accessTimestamp <= #accessTimestamp# </sql> <sql id="countSql"> select count(*) from MemberAccessLog </sql> <sql id="pageSql"> <dynamic> <isNotNull property="startIndex"> <isNotNull property="pageSize"> limit #startIndex# , #pageSize# </isNotNull> </isNotNull> </dynamic> </sql> <select id="com.fashionfree.stat.accesslog.selectMemberAccessLogBy" parameterClass="hashMap" resultMap="MemberAccessLogMap"> <include refid="selectAllSql"/> <include refid="whereSql"/> <include refid="pageSql"/> </select> <select id="com.fashionfree.stat.accesslog.selectMemberAccessLogBy.Count" parameterClass="hashMap" resultClass="int"> <include refid="countSql"/> <include refid="whereSql"/> </select> <sql id="selectAllSql"> select accessLogId, memberId, clientIP, httpMethod, actionId, requestURL, accessTimestamp, extend1, extend2, extend3 from MemberAccessLog </sql> <sql id="whereSql"> accessTimestamp <= #accessTimestamp# </sql> <sql id="countSql"> select count(*) from MemberAccessLog </sql> <sql id="pageSql"> <dynamic> <isNotNull property="startIndex"> <isNotNull property="pageSize"> limit #startIndex# , #pageSize# </isNotNull> </isNotNull> </dynamic> </sql>

说明：本例中，代码应为：

HashMap hashMap = new HashMap(); hashMap.put(“accessTimestamp”, someValue); pagedQuery(“com.fashionfree.stat.accesslog.selectMemberAccessLogBy”, hashMap);

pagedQuery方法首先去查找名为com.fashionfree.stat.accesslog.selectMemberAccessLogBy.Count 的mapped statement来进行sql查询，从而得到com.fashionfree.stat.accesslog.selectMemberAccessLogBy查询的记录个数，再进行所需的paged sql查询(com.fashionfree.stat.accesslog.selectMemberAccessLogBy)，具体过程参见utils类中的相关代码

8.sql语句中含有大于号>、小于号< 1. 将大于号、小于号写为： > < 如：

<delete id="com.fashionfree.stat.accesslog.deleteMemberAccessLogsBefore" parameterClass="long"> delete from MemberAccessLog where accessTimestamp <= #value# </delete> Xml代码 <delete id="com.fashionfree.stat.accesslog.deleteMemberAccessLogsBefore" parameterClass="long"> delete from MemberAccessLog where accessTimestamp <= #value# </delete>

将特殊字符放在xml的CDATA区内：

推荐使用第一种方式，写为< 和 > (XML不对CDATA里的内容进行解析，因此如果CDATA中含有dynamic标签，将不起作用)

9.include和sql标签将常用的sql语句整理在一起，便于共用：

<sql id="selectBasicSql"> select samplingTimestamp,onlineNum,year, month,week,day,hour from OnlineMemberNum </sql> <sql id="whereSqlBefore"> where samplingTimestamp <= #samplingTimestamp# </sql> <select id="com.fashionfree.accesslog.selectOnlineMemberNumsBeforeSamplingTimestamp" parameterClass="hashmap" resultClass="OnlineMemberNum"> <include refid="selectBasicSql" /> <include refid="whereSqlBefore" /> </select> <sql id="selectBasicSql"> select samplingTimestamp,onlineNum,year, month,week,day,hour from OnlineMemberNum </sql> <sql id="whereSqlBefore"> where samplingTimestamp <= #samplingTimestamp# </sql> <select id="com.fashionfree.accesslog.selectOnlineMemberNumsBeforeSamplingTimestamp" parameterClass="hashmap" resultClass="OnlineMemberNum"> <include refid="selectBasicSql" /> <include refid="whereSqlBefore" /> </select>

注意：sql标签只能用于被引用，不能当作mapped statement。如上例中有名为selectBasicSql的sql元素，试图使用其作为sql语句执行是错误的:

sqlMapClient.queryForList(“selectBasicSql”); ×

10.随机选取记录

<sql id=”randomSql”> ORDER BY rand() LIMIT #number# </sql>

从数据库中随机选取number条记录（只适用于MySQL）

11.将SQL GROUP BY分组中的字段拼接

<sql id=”selectGroupBy> SELECT a.answererCategoryId, a.answererId, a.answererName, a.questionCategoryId, a.score, a.answeredNum, a.correctNum, a.answerSeconds, a.createdTimestamp, a.lastQuestionApprovedTimestamp, a.lastModified, GROUP_CONCAT(q.categoryName) as categoryName FROM AnswererCategory a, QuestionCategory q WHERE a.questionCategoryId = q.questionCategoryId GROUP BY a.answererId ORDER BY a.answererCategoryId </sql> <sql id=”selectGroupBy> SELECT a.answererCategoryId, a.answererId, a.answererName, a.questionCategoryId, a.score, a.answeredNum, a.correctNum, a.answerSeconds, a.createdTimestamp, a.lastQuestionApprovedTimestamp, a.lastModified, GROUP_CONCAT(q.categoryName) as categoryName FROM AnswererCategory a, QuestionCategory q WHERE a.questionCategoryId = q.questionCategoryId GROUP BY a.answererId ORDER BY a.answererCategoryId </sql>

注：SQL中使用了MySQL的GROUP_CONCAT函数

12.按照IN里面的顺序进行排序

①MySQL:

<sql id=”groupByInArea”> select moduleId, moduleName, status, lastModifierId, lastModifiedName, lastModified from StatModule where moduleId in (3, 5, 1) order by instr(',3,5,1,' , ','+ltrim(moduleId)+',') </sql> <sql id=”groupByInArea”> select moduleId, moduleName, status, lastModifierId, lastModifiedName, lastModified from StatModule where moduleId in (3, 5, 1) order by instr(',3,5,1,' , ','+ltrim(moduleId)+',') </sql>

②SQLSERVER:

<sql id=”groupByInArea”> select moduleId, moduleName, status, lastModifierId, lastModifiedName, lastModified from StatModule where moduleId in (3, 5, 1) order by charindex(','+ltrim(moduleId)+',' , ',3,5,1,') </sql> <sql id=”groupByInArea”> select moduleId, moduleName, status, lastModifierId, lastModifiedName, lastModified from StatModule where moduleId in (3, 5, 1) order by charindex(','+ltrim(moduleId)+',' , ',3,5,1,') </sql>

说明：查询结果将按照moduleId在in列表中的顺序(3, 5, 1)来返回

MySQL : instr(str, substr)

SQLSERVER: charindex(substr, str) 返回字符串str 中子字符串的第一个出现位置 ltrim(str) 返回字符串str, 其引导(左面的)空格字符被删除

13.resultMap resultMap负责将SQL查询结果集的列值映射成Java Bean的属性值

<resultMap id="getActionIdAndActionNumber"> <result column="actionId" property="actionId" jdbcType="BIGINT" javaType="long"/> <result column="count" property="count" jdbcType="INT" javaType="int"/> </resultMap> Xml代码 <resultMap id="getActionIdAndActionNumber"> <result column="actionId" property="actionId" jdbcType="BIGINT" javaType="long"/> <result column="count" property="count" jdbcType="INT" javaType="int"/> </resultMap>

使用resultMap称为显式结果映射，与之对应的是resultClass(内联结果映射)，使用resultClass的最大好处便是简单、方便，不需显示指定结果，由iBATIS根据反射来确定自行决定。而resultMap则可以通过指定jdbcType和javaType，提供更严格的配置认证。

14.typeAlias

允许你定义别名，避免重复输入过长的名字

15.remap

<select id="testForRemap" parameterClass="hashMap" resultClass="hashMap" remapResults="true"> select userId <isEqual property="tag" compareValue="1"> , userName </isEqual> <isEqual property="tag" compareValue="2"> , userPassword </isEqual> from UserInfo </select> <select id="testForRemap" parameterClass="hashMap" resultClass="hashMap" remapResults="true"> select userId <isEqual property="tag" compareValue="1"> , userName </isEqual> <isEqual property="tag" compareValue="2"> , userPassword </isEqual> from UserInfo </select>

此例中，根据参数tag值的不同，会获得不同的结果集，如果没有remapResults="true"属性，iBatis会将第一次查询时的结果集缓存，下次再执行时（必须还是该进程中）不会再执行结果集映射，而是会使用缓存的结果集。

因此，如果上面的例子中remapResult为默认的false属性，而有一段程序这样书写：

HashMap<String, Integer> hashMap = new HashMap<String, Integer>(); hashMap.put("tag", 1); sqlClient.queryForList("testForRemap", hashMap); hashMap.put("tag", 2); sqlClient.queryForList("testForRemap", hashMap);

Java代码

则程序会在执行最后一句的query查询时报错，原因就是iBATIS使用了第一次查询时的结果集，而前后两次的结果集是不同的:(userId, userName)和(userId, userPassword)，所以导致出错。如果使用了remapResults="true"这一属性，iBATIS会在每次执行查询时都执行结果集映射，从而避免错误的发生（此时会有较大的开销）。

16.dynamic标签的prepend dynamic标签的prepend属性作为前缀添加到结果内容前面，当标签的结果内容为空时，prepend属性将不起作用。

当dynamic标签中存在prepend属性时，将会把其嵌套子标签的第一个prepend属性忽略。例如：

<sql id="whereSql"> <dynamic prepend="where "> <isNotNull property="userId" prepend="BOGUS"> userId = #userId# </isNotNull> <isNotEmpty property="userName" prepend="and "> userName = #userName# </isNotEmpty> </dynamic> </sql> <sql id="whereSql"> <dynamic prepend="where "> <isNotNull property="userId" prepend="BOGUS"> userId = #userId# </isNotNull> <isNotEmpty property="userName" prepend="and "> userName = #userName# </isNotEmpty> </dynamic> </sql>

此例中，dynamic标签中含有两个子标签<isNotNull>和<isNotEmpty>。根据前面叙述的原则，如果<isNotNull>标签中没有prepend="BOGUS" 这一假的属性来让dynamic去掉的话，<isNotEmpty>标签中的and就会被忽略，会造成sql语法错误。

注意：当dynamic标签没有prepend属性时，不会自动忽略其子标签的第一个prepend属性。

以上所述是小编给大家介绍的iBatis习惯用的16条SQL语句，希望对大家有所帮助，如果大家有任何疑问请给我们留言，小编会及时回复大家的。在此也非常感谢大家对查字典教程网的支持！