1、if
注意：test里面使用的参数，可以是mybatis的默认参数，也可以是实体属性名，但是不能是没有指定别名的参数名(尤其是单个参数，也必须起别名，否则异常);
单独使用if，如果不满足条件会SQL拼接出问题，一般我门都跟where一起使用；
select id,
cid,
name,
author,
actor,
produce,
create_date
from animes
where create_date < now()
cid = #{cid}
and author like concat('%',#{author},'%')
执行SQL:
Preparing: select id, cid, name, author, actor, produce, create_date from animes where create_date < now() and author like concat('%',?,'%')
@Test
public void testMybatisMapperDynamicSQlUserIf() throws IOException {
SqlSession defaultSqlSession = getSqlSessionFactory().openSession(true);
//获取mapper接口的代理实现类对象
AnimeMapper animeMapper = defaultSqlSession.getMapper(AnimeMapper.class);
//执行动态SQL，查询动漫列表
List animeList = animeMapper.selectAnimesByConditionUserIf(0, "土豆");
animeList.forEach(System.out::println);
}
2、where + if
*
当where标签中， if成立，增加的SQL语句，前面多出现一个and或者 or关键字，会被 自动过滤(剔除),但是 末尾出现的，不会被剔除*；
* where标签中，也可以增加固定条件，再实际开发过程中，建议where标签中，必须写固定条件，不能全部写if判断；
select id,
cid,
name,
author,
actor,
produce,
create_date
from animes
and cid = #{cid}
and author like concat('%',#{author},'%')
执行SQL:
Preparing: select id, cid, name, author, actor, produce, create_date from animes WHERE author like concat('%',?,'%')
@Test
public void testMybatisMapperDynamicSQlUserIfWhere() throws IOException {
SqlSession defaultSqlSession = getSqlSessionFactory().openSession(true);
//获取mapper接口的代理实现类对象
AnimeMapper animeMapper = defaultSqlSession.getMapper(AnimeMapper.class);
//执行动态SQL，查询动漫列表
List animeList = animeMapper.selectAnimesByConditionUserIfWhere(0, "土豆");
animeList.forEach(System.out::println);
}
3、trim + if
*
prefix: 增加前缀固定字符串；
* prefixOverrides： 前缀覆盖(自动剔除指定的关键字)；
* suffix： 增加后缀固定字符串；
* suffixOverrides： 后缀覆盖*(自动剔除指定的关键字)；
- “and |or” 中间一般都会添加一个空格；
select id,
cid,
name,
author,
actor,
produce,
create_date
from animes
cid = #{cid} and
author like concat('%',#{author},'%') and
执行SQL:
Preparing: select id, cid, name, author, actor, produce, create_date from animes where author like concat('%',?,'%') ;
@Test
public void testMybatisMapperDynamicSQlUserIfTerm() throws IOException {
SqlSession defaultSqlSession = getSqlSessionFactory().openSession(true);
//获取mapper接口的代理实现类对象
AnimeMapper animeMapper = defaultSqlSession.getMapper(AnimeMapper.class);
//执行动态SQL，查询动漫列表
List animeList = animeMapper.selectAnimesByConditionUserIfTrim(0, "土豆");
animeList.forEach(System.out::println);
}
4、set + if update
update animes
cid = #{cid},
name = #{name},
author = #{author},
actor = #{actor},
produce = #{produce},
create_date = #{createDate},
where id = #{id}
执行SQL:
Preparing: update animes SET name = ?, author = ? where id = ?
@Test
public void testMybatisMapperDynamicSQlIfSetUpd() throws IOException {
SqlSession defaultSqlSession = getSqlSessionFactory().openSession(true);
//获取mapper接口的代理实现类对象
AnimeMapper animeMapper = defaultSqlSession.getMapper(AnimeMapper.class);
//模拟前端提供更新参数，实现动态更新，给说明值，就更新什么指端
Anime animeForm = new Anime();
animeForm.setId(637);
animeForm.setName("武动乾坤KGC");
animeForm.setAuthor("土豆KGC");
int row = animeMapper.updateAnimeByConditionUserIfSet(animeForm);
System.out.println(row);
}
5、trim + if update
cid = #{cid},
name = #{name},
author = #{author},
actor = #{actor},
produce = #{produce},
create_date = #{createDate},
where id = #{id}
执行SQL:
Preparing: update animes set name = ?, author = ? where id = ?
@Test
public void testMybatisMapperDynamicSQlIfTrimUpd() throws IOException {
SqlSession defaultSqlSession = getSqlSessionFactory().openSession(true);
//获取mapper接口的代理实现类对象
AnimeMapper animeMapper = defaultSqlSession.getMapper(AnimeMapper.class);
//模拟前端提供更新参数，实现动态更新，给说明值，就更新什么指端
Anime animeForm = new Anime();
animeForm.setId(637);
animeForm.setName("武动乾坤22KGC");
animeForm.setAuthor("土豆22KGC");
int row = animeMapper.updateAnimeByConditionUserIfTrim(animeForm);
System.out.println(row);
}
6、where + choose + when (判断条件测试)
这个场景主要在 传过来的参数， 与放进SQL中的参数不一致的时候使用；
比如，前端 传过来男/女,但是数据库中查询的时候 需要使用1/2;(当然参数也可以在前端或者业务层处理好再放进SQL)
test 整体用单引号，里面的 判断条件双引号；
select id,
cid,
name,
author,
actor,
produce,
create_date
from animes
and cid = 1
and cid = 2
and cid = 3
List animeList = animeMapper.selectAnimesByConditionUserChooseWhenOtherwise("2");
执行SQL:
-- SQL正常
Preparing: select id, cid, name, author, actor, produce, create_date from animes WHERE cid = 2
-- 可以以查到正确数据
Anime(id=201, cid=2, name=海贼王, author=尾田, actor=路飞, produce=腾讯动漫, createDate=Tue Apr 05 00:00:00 CST 2022)
Anime(id=627, cid=2, name=魁拔3, author=青春树, actor=蛮吉, produce=青春树, createDate=Tue Jan 07 00:00:00 CST 2003)
test 整体用双引号，里面的 判断条件单引号；
...
and cid = 1
and cid = 2
and cid = 3
...
List animeList = animeMapper.selectAnimesByConditionUserChooseWhenOtherwise("2");
执行SQL：
-- SQL没有报错，但是 cid == 2 的条件没有成立，而是走了默认参数 cid = 3
Preparing: select id, cid, name, author, actor, produce, create_date from animes WHERE cid = 3
-- 可以查到数据，但是数据不正确，是cid=3的数据
Anime(id=301, cid=3, name=完美世界, author=辰东, actor=石昊, produce=玄机科技, createDate=Tue Apr 05 00:00:00 CST 2022)
test 整体用双引号，里面的 判断条件单引号并且判断条件加了toString()；
...
and cid = 1
and cid = 2
and cid = 3
...
List animeList = animeMapper.selectAnimesByConditionUserChooseWhenOtherwise("2");
执行SQL:
-- SQL正常
Preparing: select id, cid, name, author, actor, produce, create_date from animes WHERE cid = 2
-- 可以以查到正确数据
Anime(id=201, cid=2, name=海贼王, author=尾田, actor=路飞, produce=腾讯动漫, createDate=Tue Apr 05 00:00:00 CST 2022)
Anime(id=627, cid=2, name=魁拔3, author=青春树, actor=蛮吉, produce=青春树, createDate=Tue Jan 07 00:00:00 CST 2003)
总结：
- test 整体用单引号，里面的 判断条件双引号；
- 如果要使用test 整体用双引号，里面的 判断条件单引号，一定要加toString()；
...
and cid = 1
and cid = 2
and cid = 3
...
List animeList = animeMapper.selectAnimesByConditionUserChooseWhenOtherwise("2");
执行SQL:
-- SQL正常
Preparing: select id, cid, name, author, actor, produce, create_date from animes WHERE cid = 2
-- 可以查到正确数据
Anime(id=201, cid=2, name=海贼王, author=尾田, actor=路飞, produce=腾讯动漫, createDate=Tue Apr 05 00:00:00 CST 2022)
Anime(id=627, cid=2, name=魁拔3, author=青春树, actor=蛮吉, produce=青春树, createDate=Tue Jan 07 00:00:00 CST 2003)
...
and cid = 1
and cid = 2
and cid = 3
...
List animeList = animeMapper.selectAnimesByConditionUserChooseWhenOtherwise("2");
执行SQL:
-- SQL正常
Preparing: select id, cid, name, author, actor, produce, create_date from animes WHERE cid = 2
-- 可以查到正确数据
Anime(id=201, cid=2, name=海贼王, author=尾田, actor=路飞, produce=腾讯动漫, createDate=Tue Apr 05 00:00:00 CST 2022)
Anime(id=627, cid=2, name=魁拔3, author=青春树, actor=蛮吉, produce=青春树, createDate=Tue Jan 07 00:00:00 CST 2003)
...
and cid = 1
and cid = 2
and cid = 3
...
List animeList = animeMapper.selectAnimesByConditionUserChooseWhenOtherwise("2");
执行SQL:
-- SQL正常
Preparing: select id, cid, name, author, actor, produce, create_date from animes WHERE cid = 2
-- 可以查到正确数据
Anime(id=201, cid=2, name=海贼王, author=尾田, actor=路飞, produce=腾讯动漫, createDate=Tue Apr 05 00:00:00 CST 2022)
Anime(id=627, cid=2, name=魁拔3, author=青春树, actor=蛮吉, produce=青春树, createDate=Tue Jan 07 00:00:00 CST 2003)
...
and cid = 1
and cid = 2
and cid = 3
...
List animeList = animeMapper.selectAnimesByConditionUserChooseWhenOtherwise("2");
执行SQL:
-- SQL正常
Preparing: select id, cid, name, author, actor, produce, create_date from animes WHERE cid = 2
-- 可以查到正确数据
Anime(id=201, cid=2, name=海贼王, author=尾田, actor=路飞, produce=腾讯动漫, createDate=Tue Apr 05 00:00:00 CST 2022)
Anime(id=627, cid=2, name=魁拔3, author=青春树, actor=蛮吉, produce=青春树, createDate=Tue Jan 07 00:00:00 CST 2003)
...
and cid = 1
and cid = 2
and cid = 3
...
List animeList = animeMapper.selectAnimesByConditionUserChooseWhenOtherwise("B");
执行SQL:
-- SQL正常
Preparing: select id, cid, name, author, actor, produce, create_date from animes WHERE cid = 2
-- 可以查到正确数据
Anime(id=201, cid=2, name=海贼王, author=尾田, actor=路飞, produce=腾讯动漫, createDate=Tue Apr 05 00:00:00 CST 2022)
Anime(id=627, cid=2, name=魁拔3, author=青春树, actor=蛮吉, produce=青春树, createDate=Tue Jan 07 00:00:00 CST 2003)
...
and cid = 1
and cid = 2
and cid = 3
...
List animeList = animeMapper.selectAnimesByConditionUserChooseWhenOtherwise("B");
执行SQL:
-- SQL正常
Preparing: select id, cid, name, author, actor, produce, create_date from animes WHERE cid = 2
-- 可以查到正确数据
Anime(id=201, cid=2, name=海贼王, author=尾田, actor=路飞, produce=腾讯动漫, createDate=Tue Apr 05 00:00:00 CST 2022)
Anime(id=627, cid=2, name=魁拔3, author=青春树, actor=蛮吉, produce=青春树, createDate=Tue Jan 07 00:00:00 CST 2003)
and cid = 1
and cid = 2
and cid = 3
List animeList = animeMapper.selectAnimesByConditionUserChooseWhenOtherwise("22");
执行SQL:
-- SQL正常
Preparing: select id, cid, name, author, actor, produce, create_date from animes WHERE cid = 2
-- 可以查到正确数据
Anime(id=201, cid=2, name=海贼王, author=尾田, actor=路飞, produce=腾讯动漫, createDate=Tue Apr 05 00:00:00 CST 2022)
Anime(id=627, cid=2, name=魁拔3, author=青春树, actor=蛮吉, produce=青春树, createDate=Tue Jan 07 00:00:00 CST 2003)
...
and cid = 1
and cid = 2
and cid = 3
...
List animeList = animeMapper.selectAnimesByConditionUserChooseWhenOtherwise("22");
执行SQL:
-- SQL正常
Preparing: select id, cid, name, author, actor, produce, create_date from animes WHERE cid = 2
-- 可以查到正确数据
Anime(id=201, cid=2, name=海贼王, author=尾田, actor=路飞, produce=腾讯动漫, createDate=Tue Apr 05 00:00:00 CST 2022)
Anime(id=627, cid=2, name=魁拔3, author=青春树, actor=蛮吉, produce=青春树, createDate=Tue Jan 07 00:00:00 CST 2003)
...
and cid = 1
and cid = 2
and cid = 3
...
List animeList = animeMapper.selectAnimesByConditionUserChooseWhenOtherwise("BB");
执行SQL:
-- SQL正常
Preparing: select id, cid, name, author, actor, produce, create_date from animes WHERE cid = 2
-- 可以查到正确数据
Anime(id=201, cid=2, name=海贼王, author=尾田, actor=路飞, produce=腾讯动漫, createDate=Tue Apr 05 00:00:00 CST 2022)
Anime(id=627, cid=2, name=魁拔3, author=青春树, actor=蛮吉, produce=青春树, createDate=Tue Jan 07 00:00:00 CST 2003)
...
and cid = 1
and cid = 2
and cid = 3
...
List animeList = animeMapper.selectAnimesByConditionUserChooseWhenOtherwise("BB");
执行SQL:
-- SQL正常
Preparing: select id, cid, name, author, actor, produce, create_date from animes WHERE cid = 2
-- 可以查到正确数据
Anime(id=201, cid=2, name=海贼王, author=尾田, actor=路飞, produce=腾讯动漫, createDate=Tue Apr 05 00:00:00 CST 2022)
Anime(id=627, cid=2, name=魁拔3, author=青春树, actor=蛮吉, produce=青春树, createDate=Tue Jan 07 00:00:00 CST 2003)
...
and cid = 1
and cid = 2
and cid = 3
...
List animeList = animeMapper.selectAnimesByConditionUserChooseWhenOtherwise("任意字符2");
执行SQL:
-- SQL正常
Preparing: select id, cid, name, author, actor, produce, create_date from animes WHERE cid = 2
-- 可以查到正确数据
Anime(id=201, cid=2, name=海贼王, author=尾田, actor=路飞, produce=腾讯动漫, createDate=Tue Apr 05 00:00:00 CST 2022)
Anime(id=627, cid=2, name=魁拔3, author=青春树, actor=蛮吉, produce=青春树, createDate=Tue Jan 07 00:00:00 CST 2003)
...
and cid = 1
and cid = 2
and cid = 3
...
List animeList = animeMapper.selectAnimesByConditionUserChooseWhenOtherwise("任意字符2");
执行SQL:
-- SQL正常
Preparing: select id, cid, name, author, actor, produce, create_date from animes WHERE cid = 2
-- 可以查到正确数据
Anime(id=201, cid=2, name=海贼王, author=尾田, actor=路飞, produce=腾讯动漫, createDate=Tue Apr 05 00:00:00 CST 2022)
Anime(id=627, cid=2, name=魁拔3, author=青春树, actor=蛮吉, produce=青春树, createDate=Tue Jan 07 00:00:00 CST 2003)
只需要将test 整体用单引号，里面的 判断条件双引号，就可以，加不加.toString(),并不影响；
7、foreach
根据id集合查询动漫集合；
使用 in;
select id,
cid,
name,
author,
actor,
produce,
create_date
from animes
#{id}
执行SQL:
Preparing: select id, cid, name, author, actor, produce, create_date from animes WHERE id in( ? , ? , ? )
使用 in;
select id,
cid,
name,
author,
actor,
produce,
create_date
from animes
#{id}
执行SQL:
Preparing: select id, cid, name, author, actor, produce, create_date from animes WHERE id in( ? , ? , ? )
不用where标签;
使用 in;
select id,
cid,
name,
author,
actor,
produce,
create_date
from animes
#{id}
执行SQL:
Preparing: select id, cid, name, author, actor, produce, create_date from animes where id in( ? , ? , ? )
不用where标签;
使用 in;
通过7.1.3和7.1.4 可以总结，trim 和 foreach 都有前缀，后缀和分隔符，可以根据情况进项选择使用；
select id,
cid,
name,
author,
actor,
produce,
create_date
from animes
#{id}
执行SQL:
Preparing: select id, cid, name, author, actor, produce, create_date from animes where id in ( ? , ? , ? )
不用where标签;
使用 or;
select id,
cid,
name,
author,
actor,
produce,
create_date
from animes
id = #{id}
执行SQL:
Preparing: select id, cid, name, author, actor, produce, create_date from animes where id = ? or id = ? or id = ?
@Test
public void testMybatisMapperDynamicSQlUserForeach() throws IOException {
SqlSession defaultSqlSession = getSqlSessionFactory().openSession(true);
//获取mapper接口的代理实现类对象
AnimeMapper animeMapper = defaultSqlSession.getMapper(AnimeMapper.class);
//执行动态SQL，查询动漫列表
List animeList = animeMapper.selectAnimesByConditionUserForeach(Arrays.asList(101,102,103));
animeList.forEach(System.out::println);
}
8、trim + if insert
cid,
name,
author,
actor,
produce,
create_date,
#{cid},
#{name},
#{author},
#{actor},
#{produce},
#{createDate},
执行SQL:
insert into animes ( cid, name, author, actor, produce ) values ( ?, ?, ?, ?, ? )
@Test
public void testMybatisMapperDynamicSQlIfTrimInsert() throws IOException {
SqlSession defaultSqlSession = getSqlSessionFactory().openSession(true);
//获取mapper接口的代理实现类对象
AnimeMapper animeMapper = defaultSqlSession.getMapper(AnimeMapper.class);
Anime animeForm = new Anime();
animeForm.setCid(1);
animeForm.setName("知否知否");
animeForm.setAuthor("关心则乱");
animeForm.setActor("明兰");
animeForm.setProduce("优酷");
//指定if+ trim 冬天SQL,新增动漫
int row = animeMapper.insertAnimeByConditionIfTrim(animeForm);
System.out.println(row);
}
9、@ Select
使用注 释添加动漫；
@Select("select id,cid,name,author,actor,produce,create_date from animes where id = #{id} ")
Anime selectAnimesByConditionUserAnnotationSelect(Integer id);
执行SQL:
Preparing: select id,cid,name,author,actor,produce,create_date from animes where id = ?
@Test
public void testAnimesByConditionUserAnnotationSelect() throws IOException {
SqlSession defaultSqlSession = getSqlSessionFactory().openSession(true);
//获取mapper接口的代理实现类对象
AnimeMapper animeMapper = defaultSqlSession.getMapper(AnimeMapper.class);
Anime anime = animeMapper.selectAnimesByConditionUserAnnotationSelect(653);
System.out.println(anime);
}
10、@Delete 批量删除
@Delete({"",
"delete from animes",
"<foreach collection='ids' item='id' open=' where id in ( ' close= ' ) ' separator= ' , '> " ,
" #{id} ",
"</foreach>" ,
""})
int deleteAnimesByConditionUserAnnotationDelete(@Param("ids") List ids);
执行SQL:
Preparing: delete from animes where id in ( ? , ? , ? )
@Test
public void testDeleteAnimesByConditionUserAnnotationDelete() throws IOException {
SqlSession defaultSqlSession = getSqlSessionFactory().openSession(true);
//获取mapper接口的代理实现类对象
AnimeMapper animeMapper = defaultSqlSession.getMapper(AnimeMapper.class);
int row = animeMapper.deleteAnimesByConditionUserAnnotationDelete(Arrays.asList(649, 651, 652));
System.out.println(row);
}
11、批量加入动漫分类
insert into category (name) values
(#{category.name})
执行SQL:
Preparing: insert into category (name) values (?) , (?) , (?)
@Test
public void testInsertCategoryBatchUserFoeEach() throws IOException {
SqlSession defaultSqlSession = getSqlSessionFactory().openSession(true);
//获取mapper接口的代理实现类对象
AnimeMapper animeMapper = defaultSqlSession.getMapper(AnimeMapper.class);
Category category1 = new Category();
Category category2 = new Category();
Category category3 = new Category();
category1.setName("aaa");
category2.setName("bbb");
category3.setName("ccc");
List categoryList = new ArrayList<>();
categoryList.add(category1);
categoryList.add(category2);
categoryList.add(category3);
int row = animeMapper.insertCategoryBatchUserFoeEach(categoryList);
System.out.println(row);
}
12、排序无效问题
在使用MyBatis解析xml进行排序的时候，遇见 排序无效的问题！
-
将传入的 数据都 当成一个字符串，会对自动传入的数据 加一个双引号。
如：order by #{user_id}，如果传入的值是111,那么解析成sql时的值为order by “111”, 如果传入的值是id，则解析成的sql为order by “id”。 多加了双引号；
- $将传入的 数据直接显示生成在sql中。如：order by ${user_id}，
如果传入的值是111,那么解析成sql时的值为order by 111, 如果传入的值是id，则解析成的sql为order by id。 参数正常；
- 扩展：关于 表名，字段等等的参数， 必须使用$, 不能使用#,要不然会 预编译后，参数 多加了 双引号；
13、前端时间格式不正确问题
通过Mybatis,自动映射出来的时间，获取出来后时间格式不正确：
显示的格式为： Sat Dec 10 00:00:00 CST 1983
想要显示的格式： 1983-12-10
因为MyBatis映射的格式就有问题，所以可以 在get方法中将时间格式化；
public String getBirthday() {
return new SimpleDateFormat("yyyy-MM-dd").format(this.birthday);
}
通过格式化标签库的 进行格式化
Original: https://www.cnblogs.com/xiaoqigui/p/16619854.html
Author: 化羽羽
Title: MyBatis(三)-动态SQL
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