技术标签: java MybatisFlex mybatis
/**
* 使用QueryWrapper构建超复杂SQL语句
*/
@Test
public void testQueryWrapper1() {
QueryWrapper wrapper = QueryWrapper.create()
.select(SYS_USER_ENTITY.ALL_COLUMNS, SYS_ROLE_ENTITY.ALL_COLUMNS, SYS_MENU_ENTITY.ALL_COLUMNS)
.from(SYS_USER_ENTITY)
.leftJoin(SYS_USER_ROLE_ENTITY).on(SYS_USER_ENTITY.ID.eq(SYS_USER_ROLE_ENTITY.USER_ID))
.leftJoin(SYS_ROLE_ENTITY).on(SYS_ROLE_ENTITY.ID.eq(SYS_USER_ROLE_ENTITY.ROLE_ID))
.leftJoin(SYS_ROLE_MENU_ENTITY).on(SYS_ROLE_ENTITY.ID.eq(SYS_ROLE_MENU_ENTITY.ROLE_ID))
.leftJoin(SYS_MENU_ENTITY).on(SYS_ROLE_MENU_ENTITY.MENU_ID.eq(SYS_MENU_ENTITY.ID))
.where(SYS_USER_ENTITY.ID.gt(0))
.groupBy(SYS_USER_ENTITY.USERNAME)
.having(SYS_USER_ENTITY.USERNAME.like("a"))
.orderBy(SYS_USER_ENTITY.PASSWORD.desc())
.union(QueryWrapper.create().from(ACCOUNT))
.limit(3);
printSql(wrapper);
}
结果
SELECT
` sys_user `.*,
` sys_role `.*,
` sys_menu `.*
FROM
` sys_user `
LEFT JOIN ` sys_user_role ` ON ` sys_user `.` id ` = ` sys_user_role `.` user_id `
LEFT JOIN ` sys_role ` ON ` sys_role `.` id ` = ` sys_user_role `.` role_id `
LEFT JOIN ` sys_role_menu ` ON ` sys_role `.` id ` = ` sys_role_menu `.` role_id `
LEFT JOIN ` sys_menu ` ON ` sys_role_menu `.` menu_id ` = ` sys_menu `.` id `
WHERE
` sys_user `.` id ` > 0
GROUP BY
` sys_user `.` username `
HAVING
` sys_user `.` username ` LIKE '%a%'
ORDER BY
` sys_user `.` password ` DESC
/**
* 动态条件
*/
@Test
public void testDynamic() {
// 例如;
QueryWrapper wrapper = QueryWrapper.create().select(SYS_USER_ENTITY.ALL_COLUMNS).from(SYS_USER_ENTITY);
String name = "";
boolean flag = name != null && !name.trim().isEmpty();
// 方式一:为null或""不拼接条件
wrapper.where(flag ? SYS_USER_ENTITY.NAME.eq(name) : QueryMethods.noCondition());
// 方式二
wrapper.and(qw -> {
qw.or(SYS_USER_ENTITY.NAME.eq(name).when(flag)).or(SYS_USER_ENTITY.USERNAME.eq(name).when(StringUtil.isNotBlank(name)));
});
// 方式三
wrapper.where(SYS_USER_ENTITY.NAME.eq(name).when(If::hasText));
wrapper.and(SYS_USER_ENTITY.NAME.eq(name).when(StringUtil.isNotBlank(name)));
// 方式四
wrapper.where(SYS_USER_ENTITY.NAME.eq(name, If::hasText));
printSql(wrapper);
}
结果
SELECT
*
FROM
` sys_user `
WHERE
` name ` = 'zs'
AND ` name ` = 'zs'
AND ` name ` = 'zs'
AND (
` name ` = 'zs'
OR ` username ` = 'zs'
)
AND ` name ` = 'zs'
/**
* sql函数
*/
@Test
public void testSqlFunction1() {
QueryWrapper wrapper = QueryWrapper.create()
.select(ACCOUNT.ID, ACCOUNT.USER_NAME,
QueryMethods.max(ACCOUNT.BIRTHDAY),
QueryMethods.avg(ACCOUNT.AGE).as("avgAge"))
.from(ACCOUNT);
printSql(wrapper);
/**
* SELECT
* ` id `,
* ` user_name `,
* MAX(` birthday `),
* AVG(` age `) AS ` avgAge `
* FROM
* ` tb_account `
*/
}
@Test
public void testSqlFunction2() {
QueryWrapper wrapper = QueryWrapper.create()
.select(concat(ACCOUNT.USER_NAME, string("ly")))
.from(ACCOUNT)
.where(not(ACCOUNT.AGE.eq(3)));
printSql(wrapper);
/**
* SELECT
* CONCAT(` user_name `, 'ly')
* FROM
* ` tb_account `
* WHERE
* NOT (` age ` = 3)
*/
}
@Test
public void testLambda() {
QueryWrapper wrapper = QueryWrapper.create()
.from(Account.class)
.select(Account::getId, Account::getUserName)
.where(Account::getAge).gt(20)
.or(Account::getUserName).like("ly")
.or(Account::getBirthday).between(DateUtil.parseDate("2023-08-10"), DateUtil.parseDate("2023-08-16"));
printSql(wrapper);
}
结果
SELECT
` id `,
` user_name `
FROM
` tb_account `
WHERE
` age ` > 20
OR ` user_name ` LIKE '%ly%'
OR ` birthday ` BETWEEN '2023-08-10 00:00:00' AND '2023-08-16 00:00:00'
前面的所有操作都可以使用字符串的形式进行拼接,当然混着用也是可以的
/**
* 字符串扩展
*/
@Test
public void testString() {
long id = 1L;
QueryWrapper wrapper = QueryWrapper.create()
.select("id", "user_name", "age")
.from("tb_account")
.where("id = ?", id);
printSql(wrapper);
}
结果
SELECT
id,
user_name,
age
FROM
` tb_account `
WHERE
id = 1
用于设置修改QueryWrapper相关属性信息
@Test
public void testCPI() {
QueryWrapper wrapper = QueryWrapper.create()
.select(ACCOUNT.ALL_COLUMNS)
.from(ACCOUNT)
.where(ACCOUNT.AGE.gt(10))
.limit(10);
CPI.setLimitRows(wrapper, 1L);
printSql(wrapper);
}
查询所有列
SELECT * FROM ` tb_account `
/**
* select *
*/
@Test
public void testSelectAll() {
QueryWrapper wrapper = QueryWrapper.create()
.select(ACCOUNT.ALL_COLUMNS)
.from(ACCOUNT);
printSql(wrapper);
}
给某些列取别名
SELECT ` user_name ` AS ` user_name ` FROM ` tb_account `
/**
* select as
*/
@Test
public void testSelectAs() {
QueryWrapper wrapper = QueryWrapper.create()
.select(ACCOUNT.USER_NAME.as(Account::getUserName))
.from(ACCOUNT);
printSql(wrapper);
}
查询多张表
SELECT
` T1 `.*,
` T2 `.*
FROM
` tb_user ` AS ` T1 `,
` tb_card ` AS ` T2 `
WHERE ` T1 `.` id ` = ` T2 `.` user_id `
/**
* select multi-table
*/
@Test
public void testSelectMultiTableColumn() {
QueryWrapper wrapper = QueryWrapper.create()
.select(USER.ALL_COLUMNS, CARD.ALL_COLUMNS)
.from(USER.as("T1"), CARD.as("T2"))
.where(USER.ID.eq(CARD.USER_ID));
printSql(wrapper);
}
查询时使用函数
SELECT
MAX(` age `),
AVG(` age `),
MIN(` age `) AS ` age_avg `
FROM
` tb_user `
/**
* select function
*/
@Test
public void testSelectFunction() {
QueryWrapper wrapper = QueryWrapper.create()
.select(max(USER.AGE), avg(USER.AGE), min(USER.AGE).as("age_avg"))
.from(USER);
printSql(wrapper);
}
所有函数参考官网AllFunction
在列上做一些计算操作
SELECT
(` age ` + 10) AS ` age `,
SUM(` id ` * ` age `) AS ` total `
FROM
` tb_account `
/**
* select 列计算
*/
@Test
public void testColumnCalculation() {
QueryWrapper wrapper = QueryWrapper.create()
.select(ACCOUNT.AGE.add(10).as("age"),
sum(ACCOUNT.ID.multiply(ACCOUNT.AGE)).as("total"))
.from(ACCOUNT);
printSql(wrapper);
}
case … when条件语句
SELECT
` user_name `,
(
CASE
WHEN ` age ` >= 18 THEN '青年'
WHEN ` age ` >= 30 THEN '中年'
WHEN ` age ` >= 60 THEN '老年'
ELSE '其他'
END
) AS ` desc `
FROM
` tb_account `
/**
* select case...when
*/
@Test
public void selectCaseWhen() {
QueryWrapper wrapper = QueryWrapper.create()
.from(ACCOUNT)
.select(ACCOUNT.USER_NAME,
case_().when(ACCOUNT.AGE.ge(18))
.then("青年")
.when(ACCOUNT.AGE.ge(30))
.then("中年")
.when(ACCOUNT.AGE.ge(60))
.then("老年")
.else_("其他")
.end().as("desc")
);
printSql(wrapper);
}
查询条件
SELECT
` id `,
` age `,
` birthday `,
` user_name `
FROM
` tb_account `
WHERE
(
` id ` <= 3
OR ` age ` >= 10
)
AND ` user_name ` LIKE '张%'
/**
* where 条件
*/
@Test
public void testWhere() {
QueryWrapper wrapper = QueryWrapper.create()
.select(ACCOUNT.DEFAULT_COLUMNS)
.from(ACCOUNT)
.where(ACCOUNT.ID.le(3).or(ACCOUNT.AGE.ge(10)))
.and(ACCOUNT.USER_NAME.likeLeft("张"));
printSql(wrapper);
}
动态查询条件
SELECT
` id `,
` age `,
` birthday `,
` user_name `
FROM
` tb_account `
WHERE
` user_name ` LIKE 'zhang%'
/**
* dynamic where 条件
*/
@Test
public void testDynamicWhere1() {
boolean flag = false;
QueryWrapper wrapper = QueryWrapper.create()
.select(ACCOUNT.DEFAULT_COLUMNS)
.from(ACCOUNT)
.where(flag ? ACCOUNT.AGE.gt(10) : noCondition())
.and(ACCOUNT.USER_NAME.likeLeft("zhang"));
printSql(wrapper);
}
@Test
public void testDynamicWhere2() {
String name = "";
QueryWrapper wrapper = QueryWrapper.create()
.select(ACCOUNT.ALL_COLUMNS)
.from(ACCOUNT)
.where(ACCOUNT.USER_NAME.like(name).when(StringUtil.isNotBlank(name)));
printSql(wrapper);
}
@Test
public void testDynamicWhere3() {
String name = "aaa";
QueryWrapper wrapper = QueryWrapper.create()
.from(ACCOUNT)
.where(ACCOUNT.USER_NAME.like(name).when(If.hasText(name)))
.and(ACCOUNT.AGE.ge(10));
/**
*SELECT
* *
* FROM
* ` tb_account `
* WHERE
* ` user_name ` LIKE '%aaa%'
* AND ` age ` >= 10
*/
printSql(wrapper);
}
@Test
public void testDynamicWhere4() {
String name = "aaa";
QueryWrapper wrapper = QueryWrapper.create()
.select()
.from(ACCOUNT)
.where(ACCOUNT.ID.ge(2))
.or(ACCOUNT.USER_NAME.like(name, StringUtil.isNotBlank(name)));
/**
*SELECT
* *
* FROM
* ` tb_account `
* WHERE
* ` id ` >= 2
* OR ` user_name ` LIKE '%aaa%'
*/
printSql(wrapper);
}
子查询
SELECT
*
FROM
` tb_account `
WHERE
` id ` >= (
SELECT
` id `
FROM
` tb_account `
WHERE
` birthday ` >= '2023-08-29 15:29:15'
)
/**
* where select 类似子查询
*/
@Test
public void testWhereSelect() {
QueryWrapper wrapper = QueryWrapper.create()
.select(ACCOUNT.ALL_COLUMNS)
.from(ACCOUNT)
.where(ACCOUNT.ID.ge(
select(ACCOUNT.ID).from(ACCOUNT).where(ACCOUNT.BIRTHDAY.ge(new Date()))
));
printSql(wrapper);
}
存在|不存在
SELECT
*
FROM
` tb_account `
WHERE
` id ` >= 100
AND EXISTS (
SELECT
1
FROM
` tb_account `
WHERE
` id ` = 1
)
/**
* where exists, not exists
*/
@Test
public void testWhereExistsAndNotExists() {
QueryWrapper wrapper = QueryWrapper.create()
.from(ACCOUNT)
.where(ACCOUNT.ID.ge(100))
.and(exists( // notExists
selectOne().from(ACCOUNT).where(ACCOUNT.ID.eq(1))
));
printSql(wrapper);
}
条件连接and|or
SELECT
*
FROM
` tb_account `
WHERE
` id ` >= 1
AND (
` age ` >= 18
OR ` user_name ` LIKE '%zs%'
)
OR (
` age ` IN (20, 21, 22)
AND ` user_name ` LIKE '%a'
)
/**
* and (...) or (...)
*/
@Test
public void testAndOr() {
QueryWrapper wrapper = QueryWrapper.create()
.select(ACCOUNT.ALL_COLUMNS)
.from(ACCOUNT)
.where(ACCOUNT.ID.ge(1))
.and(ACCOUNT.AGE.ge(18).or(ACCOUNT.USER_NAME.like("zs")))
.or(ACCOUNT.AGE.in(20, 21, 22).and(ACCOUNT.USER_NAME.likeRight("a")));
printSql(wrapper);
}
分组
SELECT
*
FROM
` tb_account `
GROUP BY
` user_name `
/**
* group by
*/
@Test
public void testGroupBy() {
QueryWrapper wrapper = QueryWrapper.create()
.select(ACCOUNT.ALL_COLUMNS)
.from(ACCOUNT)
.groupBy(ACCOUNT.USER_NAME);
printSql(wrapper);
}
分组后筛选
SELECT
*
FROM
` tb_account `
GROUP BY
` age `
HAVING
` age ` > 18
/**
* having
*/
@Test
public void testHaving() {
QueryWrapper wrapper = QueryWrapper.create()
.select(ACCOUNT.ALL_COLUMNS)
.from(ACCOUNT)
.groupBy(ACCOUNT.AGE)
.having(ACCOUNT.AGE.gt(18));
printSql(wrapper);
}
连接查询
SELECT
` T1 `.` id `,
` T1 `.` age `,
` T1 `.` email `,
` T1 `.` dept_id `,
` T1 `.` user_name `,
` T1 `.` gmt_create `,
` T1 `.` gmt_modified `,
` T2 `.` id ` AS ` tb_card $ id `,
` T2 `.` card_no `,
` T2 `.` user_id `,
` T2 `.` content `
FROM
` tb_user ` AS ` T1 `
INNER JOIN ` tb_card ` AS ` T2 ` ON ` T1 `.` id ` = ` T2 `.` user_id `
LEFT JOIN ` tb_card ` ON ` T1 `.` id ` = ` T2 `.` user_id `
RIGHT JOIN ` tb_card ` ON ` T2 `.` user_id ` = ` T1 `.` id `
FULL JOIN ` tb_card ` ON ` T1 `.` id ` = ` T2 `.` user_id `
WHERE
` T1 `.` age ` > 18
/**
* test join (inner join、left join、right join、full join)
*/
@Test
public void testJoin() {
QueryWrapper wrapper = QueryWrapper.create()
.select(USER.DEFAULT_COLUMNS, CARD.DEFAULT_COLUMNS)
.from(USER).as("T1")
// inner join
.innerJoin(CARD).as("T2")
.on(USER.ID.eq(CARD.USER_ID))
// left join
.leftJoin(CARD)
.on(USER.ID.eq(CARD.USER_ID))
// right join
.rightJoin(CARD)
.on(CARD.USER_ID.eq(USER.ID))
// full join
.fullJoin(CARD)
.on(USER.ID.eq(CARD.USER_ID))
.where(USER.AGE.gt(18));
printSql(wrapper);
}
链表查询on多个条件
SELECT
` tb_user `.` id `,
` tb_user `.` age `,
` tb_user `.` email `,
` tb_user `.` dept_id `,
` tb_user `.` user_name `,
` tb_user `.` gmt_create `,
` tb_user `.` gmt_modified `
FROM
` tb_user `
LEFT JOIN ` tb_card ` ON ` tb_user `.` id ` = ` tb_card `.` user_id `
AND ` tb_user `.` id ` >= 3
WHERE
` tb_card `.` id ` > 5
/**
* join on 多个条件
*/
@Test
public void testJoinOn() {
QueryWrapper wrapper = QueryWrapper.create()
.select(USER.DEFAULT_COLUMNS)
.from(USER)
.leftJoin(CARD)
.on(
USER.ID.eq(CARD.USER_ID)
.and(USER.ID.ge(3))
).where(CARD.ID.gt(5));
printSql(wrapper);
}
join中嵌套子查询,类似产生一张中间表
SELECT
` tb_user `.` id `,
` tb_user `.` age `,
` tb_user `.` email `,
` tb_user `.` dept_id `,
` tb_user `.` user_name `,
` tb_user `.` gmt_create `,
` tb_user `.` gmt_modified `
FROM
` tb_user `
LEFT JOIN (
SELECT
` user_id `
FROM
` tb_card ` AS ` temp `
WHERE
` id ` > 3
) ON ` tb_user `.` id ` = 'temp.user_id'
WHERE
` tb_user `.` age ` > 18
GROUP BY
` tb_user `.` user_name `
HAVING
` tb_user `.` user_name ` LIKE '%Z'
/**
* join select
*/
@Test
public void testJoinSelect() {
QueryWrapper wrapper = QueryWrapper.create()
.select(USER.DEFAULT_COLUMNS)
.from(USER)
.leftJoin(
select(CARD.USER_ID).from(CARD).where(CARD.ID.gt(3)).as("temp")
).on(USER.ID.eq("temp.user_id"))
.where(USER.AGE.gt(18))
.groupBy(USER.USER_NAME)
.having(USER.USER_NAME.likeRight("Z"));
printSql(wrapper);
}
分页
limit… offset MyBatis-Flex 能够自动识别当前数据库,并根据数据库的类型生成不同的 SQL,用户也可以很轻易的通过 DialectFactory 注册(新增或改写)自己的实现方言。
SELECT
` id `,
` age `,
` birthday `,
` user_name `
FROM
` tb_account `
WHERE
` id ` > 1
ORDER BY
` id ` DESC,
` age ` ASC
LIMIT
0, 10
/**
* limit... offset MyBatis-Flex 能够自动识别当前数据库,
* 并根据数据库的类型生成不同的 SQL,用户也可以很轻易的通过 DialectFactory 注册(新增或改写)自己的实现方言。
*/
@Test
public void testLimitOffset() {
QueryWrapper wrapper = QueryWrapper.create()
.select(ACCOUNT.DEFAULT_COLUMNS)
.from(ACCOUNT)
.where(ACCOUNT.ID.gt(1))
.orderBy(ACCOUNT.ID.desc(), ACCOUNT.AGE.asc())
.limit(10)
.offset(0);
printSql(wrapper);
}
让实体属性值直接作为查询条件
SELECT
` id `,
` user_name `,
` age `,
` birthday `
FROM
` tb_account `
WHERE
` user_name ` = 'ly'
AND ` age ` = 18
/**
* Entity 转化为 QueryWrapper
* 这种方式,默认通过"and"进行连接
*/
@Test
public void testEntityToQueryWrapper() {
Account account = new Account();
account.setAge(18);
account.setUserName("ly");
QueryWrapper wrapper = QueryWrapper.create(account)
.from(ACCOUNT);
printSql(wrapper);
}
自定义操作符,让实体属性值通过and|or…进行连接
SELECT
` id `,
` user_name `,
` age `,
` birthday `
FROM
` tb_account `
WHERE
` user_name ` LIKE '%ly%'
AND ` age ` >= 18
/**
* 自定义操作符
*/
@Test
public void testEntityToQueryWrapper2() {
Account account = new Account();
account.setAge(18);
account.setUserName("ly");
SqlOperators operators = SqlOperators.of()
.set(Account::getUserName, SqlOperator.LIKE)
.set(Account::getAge, SqlOperator.GE);
QueryWrapper wrapper = QueryWrapper.create(account,operators)
.from(ACCOUNT);
printSql(wrapper);
}
在 QueryWrapper 的条件构建中,如果传入 null 值,则自动忽略该条件,
这有许多的好处,不需要额外的通过 when() 方法判断。
但是也带来一些额外的知识记忆点, 因此,正对这一点需要特别注意一下
SELECT
*
FROM
` tb_account `
WHERE
` id ` > 1
/**
* 在 QueryWrapper 的条件构建中,如果传入 null 值,则自动忽略该条件,
* 这有许多的好处,不需要额外的通过 when() 方法判断。
* 但是也带来一些额外的知识记忆点, 因此,正对这一点需要特别注意一下
*/
@Test
public void testQeuryWrapperIgnoreNull() {
String name = null;
Integer age = null;
QueryWrapper wrapper = QueryWrapper.create()
.from(ACCOUNT)
.where(ACCOUNT.AGE.eq(age))
.and(ACCOUNT.USER_NAME.like(name))
.and(ACCOUNT.ID.gt(1));
printSql(wrapper);
}
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文章浏览阅读182次。我已经完成了与人类玩家和AI玩家一起编写NIM游戏的任务 . 该游戏是“Misere”(最后一个必须选择一根棒) . 人工智能应该是使用Minimax算法,但它正在进行移动,使其失去更快,我无法弄清楚为什么 . 我已经连续几天走到了尽头 . Minimax算法的目的是不输,如果它处于失败状态,延迟失去尽可能多的动作,对吧?考虑以下:NIMBoard board =新的NIMBoard(34,2)..._nim的 misere版本
文章浏览阅读1.6k次。Mapper 是 MyBatis 中的一个重要概念,它用于封装复杂的 SQL 和参数映射关系,降低数据访问层与业务逻辑层之间的耦合度,方便后期维护和扩展。本系列教程主要基于 MyBatis3.x版本进行讲解,对 MyBatis-spring、MyBatis-mybatis、MyBatis-generator 等其他框架也会有所涉及。在 MyBatis 中,Mapper 是一个接口,这个接口提供了若干个方法,这些方法对应了我们执行数据库操作时需要执行的 SQL 语句或存储过程。_mapper @select
文章浏览阅读35次。2023年最新Python安装详细教程。_python 安装详细教程 csdn
文章浏览阅读8.3k次,点赞14次,收藏40次。将体量大的程序拆分成多个小的,功能独立的模块是开发中不可或缺的一环,开发复杂程序的核心之一就是让其变得不复杂。模块化开发可以提高代码的可维护性、可重用性、可扩展性和可测试性,从而提高了开发效率和代码质量,TypeScript沿用了JS的模块概念,在之前文章中我介绍过Node环境下的两种类型兼容,顺带提了一下目前常用的模块导入导出方式:Commonjs和ES Module,这两种方式在TS中被称为是外部模块,除此之外TS还包含了内部模块和全局模块,本文将一一介绍参考文章命名空间和模块 - TypeScript_declare module