iBatis习惯用的16条SQL语句

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：

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

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 class="java.util.HashMap" 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 class="java.util.HashMap" 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

<typeAlias alias="MemberOnlineDuration" type="com.fashionfree.stat.accesslog.model.MemberOnlineDuration" />
<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

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

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留言，小编会及时回复大家的。在此也非常感谢大家对我们网站的支持！