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--uuid 獲取方法!

replace(uuid(),'-','') ---->將uuid()中的『-』，去掉，即替換成空串；

此外upper(replace(uuid(),'-',''))用於將字元轉換為大寫

--去除重複 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/

--查詢非空字段(空欄位)

ifnull(欄位名,'')<>'' //非空

ifnull(欄位名,'')='' //空值

欄位名 is null //空值

欄位名 is not null //非空

find_in_set(欄位名, '') //空

--查詢別名不為空顯示別名, 為空顯示名稱(short_name2)

select *,(case when ifnull(short_name,'')='' then org_name else short_name end) as short_name2 from med_core.t_core_organization

--建立表

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;

--匯入txt檔案

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); --匯入txt檔案

--倒出txt檔案

select name,age,city,salary into outfile 'c:/users/administrator/desktop/data_out.txt' lines terminated by '\r\n' from person;

--批量插入資料

insert into `person`(`id`,`name`,`city`,`salary`,`age`) values (57,'張三','北京',3000,31),(58,'李四','杭州',4000,25);

--count() 函式

select count(1) from 表名 --求總個數

select count(列名) from 表名 --求總個數不包含空