mysql 多條語句合併查詢

select count(*) from matches where StartTime > 1519315200 and endtime < 1519401600 and matchtype = 1 union all
select count(*) from matches where StartTime > 1519315200 and endtime < 1519401600 and matchtype = 2 union all
select count(*) from matches where StartTime > 1519315200 and endtime < 1519401600 and matchtype = 3; 

　　

union不容許重複的值  union all 容許重複值



select distinct name from table  查詢去除重複鍵值

1.查看數據庫編碼格式

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mysql> show variables like 'character_set_database';
 2.查看數據表的編碼格式

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mysql> show create table <表名>; 3.建立數據庫時指定數據庫的字符集

mysql>create database <數據庫名> character set utf8;
4.建立數據表時指定數據表的編碼格式

create table tb_books (
    name varchar(45) not null,
    price double not null,
    bookCount int not null,
    author varchar(45) not null ) default charset = utf8;
5.修改數據庫的編碼格式

mysql>alter database <數據庫名> character set utf8;
6.修改數據表格編碼格式

mysql>alter table <表名> character set utf8;
7.修改字段編碼格式

mysql>alter table <表名> change <字段名> <字段名> <類型> character set utf8;

mysql>alter table user change username username varchar(20) character set utf8 not null;
 8.添加外鍵

mysql>alter table tb_product add constraint fk_1 foreign key(factoryid) references tb_factory(factoryid);
mysql>alter table <表名> add constraint <外鍵名> foreign key<字段名> REFERENCES <外表表名><字段名>;
9.刪除外鍵

mysql>alter table tb_people drop foreign key fk_1;
mysql>alter table <表名> drop foreign key <外鍵名>;

 

自動增長列號
select (@i:=@i+1) as ord_num,time from log,(select @i:=0)b limit 10;

增長自定義列和內容
select "0~24" as "時間段",count(1) from log

 

from_unixtime將時間戳格式化

SELECT DISTINCT userid1 from ningxia_logic.video where from_unixtime(Time) > '2017-03-24 16:40:00' and from_unixtime(Time) < '2017-03-24 18:05:00'

unix_timestamp 將格式化，轉成時間戳

yesterDate=`date +%Y%m%d -d -1day`
curDate=`date +%Y%m%d`

unix_timestamp（yesterDate）