sql复制代码CREATE TABLE test1(
   id INT(3),
   `name` VARCHAR(5),
   age INT(3)
);

sql复制代码INSERT INTO test1 VALUES(999999,'小明',12);

select * from test1 where id = 999999;

id	    name	age
999999	小明	12

sql复制代码CREATE TABLE test2(
  id INT(4),
  score DECIMAL(3,2)
);

INSERT INTO test2 VALUES(1,5.123),(2, 5.236),(3,5.1);

SELECT * FROM test2;
-- 结果
id  score  
1   5.12   
2   5.24   
3   5.10

sql复制代码insert into test2 values(4, 1000.4567);
-- 结果

查询：insert into test2 values(4, 1000.4567)

错误代码： 1264
Out of range value for column 'score' at row 1

sql复制代码CREATE TABLE test3(
   id INT(4),
  `name` VARCHAR(5),
  `remark` varchar(1000)
);

insert into test3 values(1, '小红','第一条数据');
-- 数据正常插入

id  name    remark           
1   小红  第一条数据

sql复制代码insert into test3 values(1, '这个名字真长','第二条数据');
-- 显示name字段超长
<e>查询：insert into test3 values(1, '这个名字真长','第二条数据')

错误代码： 1406
Data too long for column 'name' at row 1


INSERT INTO test3 VALUES(1, 'abcdef','第三条数据');
-- 显示还是超长
查询：INSERT INTO test3 VALUES(1, 'abcdef','第三条数据')

错误代码： 1406
Data too long for column 'name' at row 1

arduino复制代码/**
 * Cluster strategy, legal values include: failover, failfast, failsafe, failback, forking
 */
String cluster() default "";
​
public class ForkingCluster implements Cluster {
    public final static String NAME = "forking";
}

ini复制代码@Reference(interfaceName = "com.xxx.XxxService", cluster = ForkingCluster.NAME)
private XxxService xxxService;

ini复制代码<dubbo:reference cluster="failsafe" />

java复制代码@Service(cluster = FailoverCluster.NAME)
public class XxxServiceImpl implements XxxService

ini复制代码<dubbo:service cluster="failsafe" />

ini复制代码public Result doInvoke(Invocation invocation, final List<Invoker<T>> invokers, LoadBalance loadbalance) throws RpcException {
    
    // 所有服务提供者
    List<Invoker<T>> copyInvokers = invokers;
    checkInvokers(copyInvokers, invocation);
    String methodName = RpcUtils.getMethodName(invocation);
    
    // 获取重试次数。值=设置的重试次数+1
    int len = getUrl().getMethodParameter(methodName, Constants.RETRIES_KEY, Constants.DEFAULT_RETRIES) + 1;
    if (len <= 0) {
        len = 1;
    }
    
    RpcException le = null;
    List<Invoker<T>> invoked = new ArrayList<Invoker<T>>(copyInvokers.size()); 
    Set<String> providers = new HashSet<String>(len);
    
    // 进行循环调用，如果调用成功，则不再重试
    for (int i = 0; i < len; i++) {
        // 如果调用过程中，服务提供者列表发生改变，则获取新的提供者列表
        if (i > 0) {
            checkWhetherDestroyed();
            copyInvokers = list(invocation);
            // check again
            checkInvokers(copyInvokers, invocation);
        }
        
        // 根据负载均衡机制选取一个服务提供者
        Invoker<T> invoker = select(loadbalance, invocation, copyInvokers, invoked);
        invoked.add(invoker);
        RpcContext.getContext().setInvokers((List) invoked);
        try {
            // 调用成功，则返回，不再进行循环重试
            Result result = invoker.invoke(invocation);
            return result;
        } catch (RpcException e) {
            if (e.isBiz()) { // biz exception.
                throw e;
            }
            le = e;
        } catch (Throwable e) {
            le = new RpcException(e.getMessage(), e);
        } finally {
            providers.add(invoker.getUrl().getAddress());
        }
    }
    
    // 全部重试失败，抛出异常，标志调用失败
    throw new RpcException("Failed to invoke the method ");
}

typescript复制代码protected void checkInvokers(List<Invoker<T>> invokers, Invocation invocation) {
    if (CollectionUtils.isEmpty(invokers)) {
        throw new RpcException("");
    }
}

swift复制代码/**
 * Cluster. (SPI, Singleton, ThreadSafe)
 */
@SPI(FailoverCluster.NAME)
public interface Cluster {
​
    /**
     * Merge the directory invokers to a virtual invoker.
     */
    @Adaptive
    <T> Invoker<T> join(Directory<T> directory) throws RpcException;
​
}

java复制代码public class CustomCluster implements Cluster {
​
    public final static String NAME = "custom";
​
    @Override
    public <T> Invoker<T> join(Directory<T> directory) throws RpcException {
        return new CustomClusterInvoker<>(directory);
    }
​
}

scala复制代码public class CustomClusterInvoker <T> extends AbstractClusterInvoker<T> {
​
    public CustomClusterInvoker(Directory<T> directory) {
        super(directory);
    }
​
    @Override
    public Result doInvoke(Invocation invocation, List<Invoker<T>> invokers, LoadBalance loadbalance) throws RpcException {
        checkInvokers(invokers, invocation);
        // 实际场景中的容错逻辑...
        return invoker.invoke(invocation);
    }
​
}

ini复制代码custom=com.xxx.cluster.CustomCluster

ini复制代码@Reference(interfaceName = "com.xxx.XxxService", cluster = CustomCluster.NAME)
private XxxService xxxService;

java复制代码@Test
public void testBigDecimal() {
    BigDecimal origin = new BigDecimal(541253);
    BigDecimal now = new BigDecimal(12389431);

    BigDecimal val = origin.divide(now, RoundingMode.HALF_UP);
    System.out.println(val);

    origin = new BigDecimal(541253);
    now = new BigDecimal(12389431.3);
    val = origin.divide(now, RoundingMode.HALF_UP);
    System.out.println(val);

    origin = new BigDecimal(541253.4);
    now = new BigDecimal(12389431);
    val = origin.divide(now, RoundingMode.HALF_UP);
    System.out.println(val);
}

sh复制代码0
0
0.043686703610520937021487456961257

java复制代码BigDecimal origin = new BigDecimal(541253);
BigDecimal now = new BigDecimal(12389431);

BigDecimal val = origin.divide(now, 5, RoundingMode.HALF_UP);
System.out.println(val);

sh复制代码0.04369

java复制代码BigDecimal origin = new BigDecimal(541253);

java复制代码// java.math.BigDecimal#BigDecimal(int)
public BigDecimal(int val) {
    this.intCompact = val;
    this.scale = 0;
    this.intVal = null;
}

public BigDecimal(long val) {
    this.intCompact = val;
    this.intVal = (val == INFLATED) ? INFLATED_BIGINT : null;
    this.scale = 0;
}

java复制代码@Test
public void testBigDecimal() {
    BigDecimal origin = new BigDecimal(541253.0);
    BigDecimal now = new BigDecimal(12389431.1);
    BigDecimal tmp = new BigDecimal(0.0);
}

java复制代码@Test
public void testBigDecimal() {
    BigDecimal origin = new BigDecimal("541253.0");
    BigDecimal now = new BigDecimal("12389431.1");
    BigDecimal t = new BigDecimal("0.0");
}

java复制代码public class EurekaClientServerRestIntegrationTest {    
    @Test
    public void testRegistration() throws Exception {
        InstanceInfo instanceInfo = instanceInfoIt.next();
        EurekaHttpResponse<Void> httpResponse = jerseyEurekaClient.register(instanceInfo);
        assertThat(httpResponse.getStatusCode(), is(equalTo(204)));
    }
}

css复制代码因为A事务未完成的时候，事务B就读取到，C就100元，在这个基础上更新，就是最后的300元

复制代码 读已提交

markdown复制代码 相同点：
  - 都是数据由于数据读写顺序，造成的数据读取前后不一致造成的


 不同点：
 
 -  1. 不可重复读-->因为特定条件下，读取的数据因为被其他事务修改或者删除，导致的数据不一致的情况（行锁）
 
 
 - 2. 幻读--> 在特定条件下，读取之前已经读取过的数据，但是发现有新的符合条件的数据（存在新数据），导致数据不一致。
 
 串行化解决

sql复制代码show index from t_user;

sql复制代码drop index 索引名 on 表名

sql复制代码create table t_user(id varchar(20) primary key,name varchar(20),key(name)

sql复制代码create index name_index on t_user(name);

sql复制代码create table t_user(id varchar(20) primary key,name varchar(20),unique(name))

sql复制代码create unique index on t_user

sql复制代码CREATE TABLE tb_test2(
  id INT,
  `name` VARCHAR(200),
  age INT,
  KEY(`name`,age)
)

sql复制代码create index name_age_index on t_user(name,age)

sql复制代码name bir age	可以
name age bir	可以
age bir			不可以
bir age name	可以
age bir			不可以

sql复制代码CREATE TABLE employees (
	id int(11) NOT NULL AUTO_INCREMENT,
	name varchar(24) NOT NULL DEFAULT '' COMMENT '姓名',
	age int(11) NOT NULL DEFAULT '0' COMMENT '年龄',
	position varchar(20) NOT NULL DEFAULT '' COMMENT '职位',
	hire_time timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '入职时间',
	PRIMARY KEY (id),
	KEY idx_name_age_position USING BTREE (name, age, position)
) ENGINE = InnoDB AUTO_INCREMENT = 4 CHARSET = utf8 COMMENT '员工记录表';

INSERT INTO employees (name, age, position, hire_time) VALUES ('LiLei', 22, 'manager', NOW());

INSERT INTO employees (name, age, position, hire_time) VALUES ('HanMeimei', 23, 'dev', NOW());

INSERT INTO employees (name, age, position, hire_time) VALUES ('Lucy', 23, 'dev', NOW());

sql复制代码EXPLAIN SELECT * FROM employees WHERE name= 'LiLei';

sql复制代码EXPLAIN SELECT * FROM employees WHERE name= 'LiLei' AND age = 22;

sql复制代码EXPLAIN SELECT * FROM employees WHERE name= 'LiLei' AND age = 22 AND position ='manager';

sql复制代码EXPLAIN SELECT * FROM employees WHERE age = 22 AND position ='manager';

sql复制代码EXPLAIN SELECT * FROM employees WHERE position = 'manager';

sql复制代码EXPLAIN SELECT * FROM employees WHERE name = 'LiLei';

sql复制代码EXPLAIN SELECT * FROM employees WHERE name = 'LiLei';

sql复制代码EXPLAIN SELECT * FROM employees WHERE left(name,3) = 'LiLei';

sql复制代码EXPLAIN SELECT * FROM employees WHERE name= 'LiLei' AND age = 22 AND position ='manager';

sql复制代码EXPLAIN SELECT * FROM employees WHERE name= 'LiLei' AND age > 22 AND position ='manager';

sql复制代码EXPLAIN SELECT * FROM employees WHERE name= 'LiLei' AND age = 23 AND position ='manager';

sql复制代码EXPLAIN SELECT * FROM employees WHERE name != 'LiLei';

sql复制代码EXPLAIN SELECT * FROM employees WHERE name is null;

sql复制代码EXPLAIN SELECT * FROM employees WHERE name like '%Lei';

sql复制代码EXPLAIN SELECT * FROM employees WHERE name like 'Lei%';

sql复制代码EXPLAIN SELECT name,age,position FROM employees WHERE name like '%Lei%';

sql复制代码EXPLAIN SELECT * FROM employees WHERE name = '1000';

sql复制代码EXPLAIN SELECT * FROM employees WHERE name = 1000;

sql复制代码EXPLAIN SELECT * FROM employees WHERE name = 'LiLei' or name = 'HanMeimei';

mysql复制代码CREATE
    [DEFINER = { user | CURRENT_USER }]
　PROCEDURE sp_name ([proc_parameter[,...]])
    [characteristic ...] routine_body
 
proc_parameter:
    [ IN | OUT | INOUT ] param_name type
 
characteristic:
    COMMENT 'string'
  | LANGUAGE SQL
  | [NOT] DETERMINISTIC
  | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
  | SQL SECURITY { DEFINER | INVOKER }
 
routine_body:
　　Valid SQL routine statement
 
[begin_label:] BEGIN
　　[statement_list]
　　　　……
END [end_label]

mysql复制代码DELIMITER $$
或
DELIMITER //

mysql复制代码CREATE PROCEDURE demo_in_parameter(IN p_in int)

mysql复制代码BEGIN .... END

mysql复制代码[begin_label:] BEGIN
　　[statement_list]
END [end_label]

mysql复制代码SET @p_in=1

mysql复制代码-- Declere 变量名 数据类型...
DECLARE l_int int unsigned default 4000000;

mysql复制代码CREATE PROCEDURE 存储过程名（参数）

mysql复制代码CREATE FUNCTION 存储函数名（参数）

mysql复制代码CREATE DEFINER=`root`@`localhost` 
PROCEDURE `mysql_scirpt`.`01.CreateStorage`( IN `01.创建存储过程` VARCHAR ( 50 ) )

BEGIN
#Routine body goes here...
SELECT
	AVG( prod_price ) AS "商品平均值" 
FROM
	products;

END

mysql复制代码{ CALL mysql_scirpt.`01.CreateStorage`(:01_创建存储过程) }

mysql复制代码USE mysql_scirpt;

DROP PROCEDURE IF EXISTS mysql_scirpt.myTry;

DELIMITER //
CREATE PROCEDURE myTry(IN 表名 varchar(50))

BEGIN
	pass...
END

DELIMITER ;

mysql复制代码DROP PROCEDUCE/FUNCTION xxx

mysql复制代码DROP PROCEDURE myTry

mysql复制代码SHOW CREATE PROCEDURE XXX;

mysql复制代码SHOW PROCEDURE STATUS LIEK 'XXX';

mysql复制代码DECLARE var_name[,...] type [DEFAULT value]

mysql复制代码DROP PROCEDURE IF EXISTS mysql_scirpt.`03.CreateVariable`;

DELIMITER $$
$$
CREATE PROCEDURE mysql_scirpt.`03.CreateVariable`(OUT num1 int)
BEGIN
	DECLARE num2 int DEFAULT 200;
	SET num1 = num2;
END$$
DELIMITER ;

CALL `03.CreateVariable`(@num);
SELECT @num;

mysql复制代码CALL `03.CreateVariable`(@num);
SELECT @num;

mysql复制代码IF expression THEN 
   statements;
END IF;

mysql复制代码IF expression THEN
   statements;
ELSE
   else-statements;
END IF;

mysql复制代码IF expression THEN
   statements;
ELSEIF elseif-expression THEN
   elseif-statements;
...
ELSE
   else-statements;
END IF;

mysql复制代码DROP PROCEDURE IF EXISTS mysql_scirpt.`04.CreateIF`;

/* 需求：
 * 180身高 -- 高
 * 170-180身高 - 中
 * 170以下 - 一般
 * */

DELIMITER $$
$$
CREATE PROCEDURE mysql_scirpt.`04.CreateIF`()
BEGIN
	DECLARE height int DEFAULT 175;
	DECLARE description varchar(50);
	
	IF height >= 180 THEN
		SET description = "高";
	ELSEIF height >=170 AND height < 180 THEN 
		SET description = "中";
	ELSE 
		SET description = "一般";
	END IF;
	
	SELECT description;
END$$
DELIMITER ;

CALL mysql_scirpt.`04.CreateIF`();

mysql复制代码create procedure procedure_name([in/out/inout] 参数名   参数类型)

mysql复制代码DROP PROCEDURE IF EXISTS mysql_scirpt.`05.CreateParameter`;

DELIMITER $$
$$
CREATE PROCEDURE mysql_scirpt.`05.CreateParameter`(IN height int)
BEGIN
	DECLARE description varchar(50) DEFAULT '';
	
	IF height >= 180 THEN
		SET description = "高";
	ELSEIF height >=170 AND height < 180 THEN 
		SET description = "中";
	ELSE 
		SET description = "一般";
	END IF;
	
	SELECT concat('身高：',height,'身材：',description) AS '描述';

END$$
DELIMITER ;

mysql复制代码{ CALL mysql_scirpt.`05.CreateParameter`(这里输入身高) }

mysql复制代码DROP PROCEDURE IF EXISTS mysql_scirpt.`06.CreateParamOut`;

DELIMITER $$
$$
CREATE DEFINER=`root`@`localhost` PROCEDURE `mysql_scirpt`.`06.CreateParamOut`(
	OUT id int
)
BEGIN
	SELECT id AS id_inner_1; -- 1.结果 1
	IF id IS NOT NULL THEN -- 3.因为 OUT参数，我们无法获取外部传来的值
		SET id = id + 1;
		SELECT id AS id_inner_2;
	ELSE
		SELECT 1 INTO id; -- 4.进入ELSE语句，将id赋值为 1
	END IF;
	
	SELECT id AS id_inner_3; -- 2.结果 2

END$$
DELIMITER ;

SET @id = 10;
CALL `mysql_scirpt`.`06.CreateParamOut`(@id);
SELECT @id AS id_out; -- 5. 最后拿到 id 为 1

mysql复制代码mysql> set @id = 10;
mysql> call pr_param_out(@id);
+------------+
| id_inner_1 |
+------------+
|       NULL |
+------------+
+------------+
| id_inner_3 |
+------------+
|          1 |
+------------+
 
mysql> select @id as id_out;
+--------+
| id_out |
+--------+
| 1      |
+--------+

mysql复制代码DROP PROCEDURE IF EXISTS mysql_scirpt.`07.CreateParamInOut`;

DELIMITER $$
$$
CREATE PROCEDURE mysql_scirpt.`07.CreateParamInOut`(
	INOUT id int
)
BEGIN
	SELECT id AS id_inner_1; -- 2. id = 10
	
	IF id IS NOT NULL THEN
		SET id = id+1; - 2. id+1 = 11
		SELECT id AS id_inner_2; -- 3. id = 11
	ELSE
		SELECT 1 INTO id;
	END IF;
	
	SELECT id AS id_inner_3; -- 4. id = 11

END$$
DELIMITER ;

SET @id = 10;
CALL mysql_scirpt.`07.CreateParamInOut`(@id); -- 1. 传入参数
SELECT @id AS id_out; -- 5. id = 11

mysql复制代码mysql> set @id = 10;
mysql> call pr_param_inout(@id);
+------------+
| id_inner_1 |
+------------+
|         10 |
+------------+
+------------+
| id_inner_2 |
+------------+
|         11 |
+------------+
+------------+
| id_inner_3 |
+------------+
|         11 |
+------------+
mysql> select @id as id_out;
+--------+
| id_out |
+--------+
| 11     |
+--------+

mysql复制代码CASE case_value
    WHEN when_value THEN statement_list
    [WHEN when_value THEN statement_list] ...
    [ELSE statement_list]
END CASE

mysql复制代码DROP PROCEDURE IF EXISTS mysql_scirpt.`08.CreateCaseOne`;

DELIMITER $$
$$
CREATE PROCEDURE mysql_scirpt.`08.CreateCaseOne`()
BEGIN
	DECLARE num int DEFAULT 3; -- 1. 给了num一个默认值 3
	
	CASE num -- 2. 条件判断 num
		WHEN 2 THEN SELECT num; -- num为2是结果为其本身
		WHEN 3 THEN SELECT 0; -- num为3是结果输出0
	END CASE;

END$$
DELIMITER ;

mysql复制代码CASE
    WHEN search_condition THEN statement_list
    [WHEN search_condition THEN statement_list] ...
    [ELSE statement_list]
END CASE

mysql复制代码DROP PROCEDURE IF EXISTS mysql_scirpt.`09.CreateCaseTwo`;

DELIMITER $$
$$
CREATE PROCEDURE mysql_scirpt.`09.CreateCaseTwo`(
	IN p1 int,
	IN p2 int,
	OUT p3 int
)
BEGIN
	CASE  -- 2. 进行判断
		WHEN p1 > p2 THEN SET p3 = 1;
		WHEN p1 = p2 THEN SET p3 = 2;
		ELSE SET p3 = 3;
	END CASE;
	SELECT p3; -- 输出
END$$
DELIMITER ;
CALL mysql_scirpt.`09.CreateCaseTwo`(200,100,@p3); -- 1. 传入参数
SELECT @p3; -- 输出

mysql复制代码[begin_label:] WHILE search_condition DO
    statement_list;
END WHILE [end_label];

mysql复制代码DROP PROCEDURE IF EXISTS mysql_scirpt.`10.CreateWhile`;

DELIMITER $$
$$
CREATE PROCEDURE mysql_scirpt.`10.CreateWhile`(IN n int)
BEGIN
	DECLARE total int DEFAULT 0;
	DECLARE num int DEFAULT 1;
	
	WHILE num<=n do -- 条件语句
		SET total = total + num;
		SET num = num + 1; -- num 递增，不写则进入死循环
	END WHILE;

	SELECT total;

END$$
DELIMITER ;

CALL mysql_scirpt.`10.CreateWhile`(10);

mysql复制代码[begin_label:] REPEAT
    statement_list
UNTIL search_condition
END REPEAT [end_label]

mysql复制代码DROP PROCEDURE IF EXISTS mysql_scirpt.`11.CcreateRepeat`;

DELIMITER $$
$$
CREATE PROCEDURE mysql_scirpt.`11.CcreateRepeat`(IN n int)
BEGIN
	DECLARE total int DEFAULT 0;
	
	REPEAT 
		SET total = total + n;
		SET n = n - 1;
		until n = 0
	END REPEAT;

	SELECT total;
	
END$$
DELIMITER ;

CALL mysql_scirpt.`11.CcreateRepeat`(10)

mysql复制代码[begin_label:] LOOP
    statement_list ;
END LOOP [begin_label];

mysql复制代码LEAVE  label ;

mysql复制代码DROP PROCEDURE IF EXISTS mysql_scirpt.`12.CreateLoopAndLeave`;

DELIMITER $$
$$
CREATE PROCEDURE mysql_scirpt.`12.CreateLoopAndLeave`(
	IN n int
)
BEGIN
	DECLARE total int DEFAULT 0;
	-- ins：begin_label
	ins: LOOP
		IF n <= 0 THEN
			LEAVE ins;
		END IF;
	
	SET total = total + n;
	SET n = n -1;
	
	END LOOP ins;
	
	SELECT total;

END$$
DELIMITER ;

CALL mysql_scirpt.`12.CreateLoopAndLeave`(10);

mysql复制代码ITERATE  label;

mysql复制代码DECLARE cursor_name CURSOR FOR select_statement;

mysql复制代码OPEN cursor_name;

mysql复制代码FETCH cursor_name INTO var_name...；(...表示可以有多个)

mysql复制代码CLOSE cursor_name;

mysql复制代码create table emp(
  id int(11) not null auto_increment ,
  name varchar(50) not null comment '姓名',
  age int(11) comment '年龄',
  salary int(11) comment '薪水',
  primary key(`id`)
)engine=innodb default charset=utf8 ;

insert into emp(id,name,age,salary) values(null,'金毛狮王',55,3800),(null,'白眉鹰王',60,4000),(null,'青翼蝠王',38,2800),(null,'紫衫龙王',42,1800);

mysql复制代码DROP PROCEDURE IF EXISTS mysql_scirpt.`13.CreateCursor`;

DELIMITER $$
$$
-- 查询emp表中数据, 并逐行获取进行展示
CREATE PROCEDURE mysql_scirpt.`13.CreateCursor`()
BEGIN
	-- 声明变量
	DECLARE e_id int(11);
	DECLARE e_name varchar(50);
	DECLARE e_age int(11);
	DECLARE e_salary int(11);
	-- 设置光标
	DECLARE emp_result CURSOR FOR SELECT * FROM emp;
	-- 开启光标
	OPEN emp_result;

	-- 捕获光标
	FETCH emp_result INTO e_id,e_name,e_age,e_salary;
	SELECT concat('id=',e_id,',name=',e_name,',age=',e_age,',salary=',e_salary);

	-- 关闭光标
	CLOSE emp_result;
END$$
DELIMITER ;

mysql复制代码DROP PROCEDURE IF EXISTS mysql_scirpt.`14.CreateGetCursor`;

DELIMITER $$
$$
CREATE PROCEDURE mysql_scirpt.`14.CreateGetCursor`()
BEGIN
	
 	DECLARE id int(11);
 	DECLARE name varchar(50);
 	DECLARE age int(11);
 	DECLARE salary int(11);
	DECLARE has_data int default 1;

	DECLARE emp_result CURSOR FOR SELECT * FROM emp;
	DECLARE EXIT handler FOR NOT FOUND SET has_data = 0;
	
	OPEN emp_result;
	
	REPEAT
		FETCH emp_result INTO id ,name,age,salary;
		SELECT concat('id=',id,',name=',name,',age=',age,',salary=',salary);
		until has_data = 0
	END REPEAT;

	CLOSE emp_result;

END$$
DELIMITER ;

mysql复制代码ERROR 1418 (HY000): This function has none of DETERMINISTIC, NO SQL, or READS SQL DATA in its declaration and binary logging is enabled (you might want to use the less safe log_bin_trust_function_creators variable)

mysql复制代码set global log_bin_trust_function_creators=TRUE;

mysql复制代码CREATE FUNCTION fn_name ([func_parameter[...]])
RETURNS type
[characteristic ...] routine_body

mysql复制代码DROP FUNCTION IF EXISTS mysql_scirpt.`15.CreateFunction`;

DELIMITER $$
$$
CREATE FUNCTION mysql_scirpt.`15.CreateFunction`(vendID int)
RETURNS INT
BEGIN
	
	DECLARE num int;
	SELECT count(*) INTO num FROM products WHERE vend_id = vendID;
	
	RETURN num;
END$$
DELIMITER ;

SELECT mysql_scirpt.`15.CreateFunction`(1001);

java复制代码@Slf4j
public class BioTest {

    /**
     * 流的形式操作文件
     */
    @Test
    public void streamTest() throws Exception {

        // 定义两个文件，in.txt 和 out.txt（提前在src目录下创建好两个文件）
        File inFile = new File("src/in.txt");
        File outFile = new File("src/out.txt");

        // 定义一个对 in.txt 操作的流对象
        InputStream inputStream = new FileInputStream(inFile);
        // 开始读取文件
        byte[] bytes = new byte[8];
        inputStream.read(bytes);
        System.out.println(new String(bytes));

        // 定义 out.txt 操作的流对象
        OutputStream outputStream = new FileOutputStream(outFile);
        // 开始写出文件
        outputStream.write(bytes);
        outputStream.write("\nout-write".getBytes(StandardCharsets.UTF_8));

    }

    /**
     * 阻塞形式操作网络编程
     */
    @Test
    public void blockTest() throws Exception {
        /*
        1、运行服务端发现，服务端在获取客户端连接及获取客户端数据时，都会堵塞
        */
    }

    @Test
    public void server() throws Exception {
        // 创建服务端对象
        ServerSocket serverSocket = new ServerSocket(9528);
        log.info("创建了一个服务端对象,{}", serverSocket);
        // 获取客户端链接的 soclet 对象
        Socket accept = serverSocket.accept();
        log.info("获取到了客户端连接对象,{}", accept);
        InputStream inputStream = accept.getInputStream();
        byte[] bytes = new byte[100];
        inputStream.read(bytes);
        log.info("客户端发来的内容：{}", new String(bytes));
    }

    @Test
    public void client() throws Exception {
        // 创建客户端，指定服务端ip及端口，进行连接
        Socket client = new Socket("localhost", 9528);
        log.info("客户端创建完毕,{}", client);
        // 开始向务端发送消息
        OutputStream outputStream = client.getOutputStream();
        outputStream.write("hello world!".getBytes(StandardCharsets.UTF_8));
    }
}

java复制代码@Slf4j
public class NioTest {

    @Test
    public void serverTest() throws Exception{
        //创建serverSocketChannel
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        //绑定端口
        serverSocketChannel.socket().bind(new InetSocketAddress(6666));
        //设置为非阻塞
        serverSocketChannel.configureBlocking(false);
        //得到Selector对象
        try (Selector selector = Selector.open()) {
            //把ServerSocketChannel注册到selector，事件为OP_ACCEPT
            serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
            //如果返回的>0，表示已经获取到关注的事件
            while (selector.select() > 0) {
                Set<SelectionKey> selectionKeys = selector.selectedKeys();
                Iterator<SelectionKey> iterator = selectionKeys.iterator();
                while (iterator.hasNext()) {
                    //获得到一个事件
                    SelectionKey next = iterator.next();
                    //如果是OP_ACCEPT，表示有新的客户端连接
                    if (next.isAcceptable()) {
                        //给该客户端生成一个SocketChannel
                        SocketChannel accept = serverSocketChannel.accept();
                        accept.configureBlocking(false);
                        //将当前的socketChannel注册到selector，关注事件为读事件，同时给socket Channel关联一个buffer
                        accept.register(selector, SelectionKey.OP_READ, ByteBuffer.allocate(1024));
                        log.info("获取到一个客户端连接");
                        //如果是读事件
                    } else if (next.isReadable()) {
                        //通过key 反向获取到对应的channel
                        SocketChannel channel = (SocketChannel) next.channel();
                        //获取到该channel关联的buffer
                        ByteBuffer buffer = (ByteBuffer) next.attachment();
                        while (channel.read(buffer) != -1) {
                            buffer.flip();
                            log.info(new String(buffer.array(), 0, buffer.limit()));
                            buffer.clear();
                        }
                    }
                    // 这个很重要，在处理完事件之后，要移除该事件
                    iterator.remove();
                }
            }
        }

    }

    @Test
    public void clientTest() throws Exception{
        //得到一个网络通道
        SocketChannel socketChannel = SocketChannel.open();
        //设置为非阻塞
        socketChannel.configureBlocking(false);
        //提供服务器端的IP和端口
        InetSocketAddress inetSocketAddress = new InetSocketAddress("localhost", 9528);
        //连接服务器
        if (!socketChannel.connect(inetSocketAddress)) {
            while (!socketChannel.finishConnect()) {
                log.info("连接需要时间,客户端不会阻塞...你可以去干别的事情了");
            }
        }
        //连接成功,发送数据
        String str = "J3-白起";
        ByteBuffer byteBuffer = ByteBuffer.wrap(str.getBytes());
        socketChannel.write(byteBuffer);
        socketChannel.close();
        log.info("客户端退出");
    }

}