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  • mysql经验

    --UUID 获取方法!
    replace(uuid(),'-','') ---->将uuid()中的‘-’,去掉,即替换成空串;
    此外
    upper(replace(uuid(),'-',''))用于将字符转换为大写

    --去除重复 DISTINCT
    SELECT DISTINCT PWD FROM t_core_resident_user WHERE EMPI='8A41B722524411E6B006000C29946D7C' //去重

    --排序
    order by ID desc/asc --排序 倒序/

    --查询非空字段(空字段)
    IFNULL(字段名,'')<>'' //非空
    IFNULL(字段名,'')='' //空值
    字段名 IS NULL //空值
    字段名 IS NOT NULL //非空
    FIND_IN_SET(字段名, '') //空

    --查询别名 不为 空显示别名, 为空显示名称(SHORT_NAME2)
    SELECT *,(CASE WHEN IFNULL(SHORT_NAME,'')='' THEN ORG_NAME ELSE SHORT_NAME END) AS SHORT_NAME2 FROM med_core.t_core_organization

    --创建表
    CREATE TABLE person(
    id INT NOT NULL AUTO_INCREMENT,
    NAME VARCHAR(40) NOT NULL,
    city VARCHAR(20),
    salary INT,
    age INT,
    PRIMARY KEY(id)
    )ENGINE=INNODB CHARSET=gb2312;

    --导入txt文件
    LOAD DATA LOCAL INFILE 'C:/Users/Administrator/Desktop/person3.txt' INTO TABLE person CHARACTER SET 'gb2312'(NAME,age,city,salary);
    LOAD DATA LOCAL INFILE 'C:/Users/Administrator/Desktop/data3.txt' INTO TABLE t0 CHARACTER SET 'utf8'(NAME,age,description); --导入txt文件

    --倒出txt文件
    SELECT NAME,age,city,salary INTO OUTFILE 'C:/Users/Administrator/Desktop/data_out.txt' LINES TERMINATED BY ' ' FROM person;
    --批量插入数据
    insert into `person`(`id`,`name`,`city`,`salary`,`age`) values (57,'张三','北京',3000,31),(58,'李四','杭州',4000,25);

    --Count() 函数
    select count(1) from 表名 --求总个数
    select count(列名) from 表名 --求总个数不包含空

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  • 原文地址:https://www.cnblogs.com/futao123/p/5939652.html
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