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：

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