數據管理:(管理表記錄)
數據導入:把系統文件的內容存儲到數據庫的表裏.
mysql> create table uesr(
-> name varchar(50),
-> mima char(1),
-> UID int(2),
-> GID int(2),
-> ms varchar(100),
-> honame char(100),
-> jsq char(25),
-> index(name)
-> );
查看默認使用目錄及目錄是否存在: show variables inke "secure_file_priv"
格式: load data infile "系統目錄/文件名" into table 庫名.表名 fields treminated by "字段間隔符號" lines treminated by "\n" 數據導入
例: load data infile "/var/lib/mysql-files/passwd" into table uesr fields terminated by ":" lines terminated by "\n" 格式 "\n";
系統目錄/文件名 表名 指定分隔符 "字段間隔符號" 列指定的分隔符是"\n"
添加一個行號方便後續工作的查找:alter table uesr add id int(2) primary key auto_increment first;
表名 添加 ID 類型
注意事項:
字段分隔符要與文件內的一致
指定導入文件的絕對路徑
導入數據的表字段類型要與文件字段匹配
禁用SElinux
數據導出:把表記錄存儲到系統文件裏.
select 查詢 into outfile "目錄/文件名"; [fields terminated by "符號" lines terminated by "符號"];
select id,name from uesr into outfile "/var/lib/mysql-files/uesr1.txt"
格式:
注意事項:導出的內容是由SQL查詢語句
limit 選取第5行
lines terminated by "\n" 行分隔符
fields terminated by "分隔符" 字段分隔符
管理表記錄:
增: insert into 庫.表 values(字段值列表); #(一次給一個字段賦值)
insert into 庫.表 (字段值列表) values (字段值列表); ##(指定字段賦值)
查:
select 字段名列表 from 庫.表 wher 條件 #全部查詢.並且條件匹配 寫wher 條件的話就是匹配表中什麼條件裏的.
select 字段名列表 (列) from 庫.表 where 條件(行) ; //指定查找
條件匹配的表示方式:
數值比較 > >= < <= = !=
字段名 符號 值
例: select name from uesr where uid=15; # 查多個時可用逗號分隔.
字符比較: = !=
字段名 符號 "值"
select name,shell from uesr where shell!="/bin/bash";
select name from uesr where name="apache";
範圍內匹配
字段名 in (值列表) 在.....裏
select id,name from user where name in("apache","root","bob");
select id,name,uid from uesr where uid in (10,15,9,12);
字段名 between 值1 and 值2 在....之間
select from user where id between 10 and 15;
select from user where uid between 1 and 10;
字段名 not in (值列表) 不在 .......裏
select name from user where uid not in(0,1,5,7)
select from user where name not in("root","mysql","bin")
匹配空 is null
字段名 is null
select id from uesr where name is null;
匹配非空 is not null
字段名 is not null
select id,name.shell from uesr where shell is not null;
select id,name from user where name="";
select id,name from user where name="null";
distinct不顯示重賦值
distinct 字段名
select destinct shell from user;
關鍵字
select distinct shell from user where uid<=10;
邏輯匹配: 有多個條件匹配
邏輯與 && and多個條件必須都成立
邏輯或 || or多個條件有一個條件成立即可.
邏輯非 ! 取反.
條件1 &&條件2 條件n 可以用&&連接(三個條件都有)
select name from uesr where name ="zhangsan"and uid=500 and shell="/bin/bash";
表名 列名 內容 與 列名條件 與 列名條件
select name from uesr where name ="zhangsan" or uid=500 or shell="/bin/bash";
運算操作: + - / %
select 字段名 符號 字段名 from 表名 where 條件;
例:
select UID + GID from uesr where name="root";
select UID,GID,UID + GID he from uesr where name="root";
模糊查詢: like
where 字段名 like '表達式'; ###一般情況下表達式可以用
任意一個字符
% 0個或者多個字符
select name from uesr where name like '___' and UID<=10;
select name from uesr where name like 'a%'; ##用戶名裏有a的
select id,name from uesr where name like '%%'; ##包含任意字符的
select name from uesr where name in ("","null") or name is null; #### 匹配空,或者空的名,
正則匹配
where 字段名 regexp '正則表達式';
. ^ $ [ ]
insert into uesr(name)values("bob9"),("j7im"),("1yaya");
select name from uesr where name regexp '[0-9]$'; 數字結尾的名字
select name from uesr where name regexp '^[0-9]'; 數字在前的名字
select name from uesr where name regexp '..'; 任意字符和數字的
select name,uid from uesr where uid regexp '^..$';
select name,uid from user where name regexp 'a.t'
select * from uesr where name regexp '^r|t$'; 查出r開頭t結尾的
統計函數:
求和, 求平均值, 求最大值, 求最小值 統計個數
sum(字段名) avg(字段名) max(字段名) min(字段名) count(字段名)
select count(name) from uesr where jsq="/bin/bash"; #統計
select max(uid) from uesr; #求最大值
select min(gid) from uesr; #求最小值
select avg(age) from uesr; #平均值
select sum(gid) from uesr; #求和
select sum(uid),count(name) from uesr; ##求和統計
查詢排序 order by
sql查詢 order by 字段名 desc;(asc/desc) #默認升序
select name,uid from uesr where uid between 10 and 50 order by uid desc; 降序
select name,uid from uesr where uid between 10 and 50; 默認升序
查詢分組 group by
sql查詢 group by 字段名
select shell from user where uid between 10 and 50; 10到50行不顯示重複的組,
select 字段名 from 表名 where 字段名 between 10 and 50 group by 字段名;
查詢限制行數 limit
sql查詢 limit 數字; 顯示查詢結果的前幾行
select * from uesr limit 1 顯示查詢結果的第一行
sql查詢 limit 數字1 , 數字2 ; 設置顯示行的範圍
select from user; 顯示所有
select from user limit 2; 顯示行
select * from user limit 2,5; 顯示行的範圍
select * from uesr order by uid desc limit 5; #uid用戶最大的前五個顯示出來
改:
條件匹配的表示方式:
數值比較 字符比較 範圍內匹配 匹配空 匹配非空 邏輯匹配
正則匹配 模糊查詢
去掉字段重賦值 數字計算 統計函數 分組 排序 限制行數.
單表查詢:select 字段名列表 from 庫.表 wher 條件
where嵌套查詢:把內存的查詢結果作爲外層查詢的查詢條件
格式:select 字段名列表 from 表名 where 條件 ( );
#顯示用戶名和uid號 uid字段的值要大於uid字段的平均值
select name,uid from uesr where uid > (select avg(uid) from uesr); ##同庫同表
select name from uesr where name not in (select user from mysql.user); ###不同庫不同表
select name from uesr where name in (select user from mysql.user where user="zhangsan");
select name from user where name not in (select user from mysql.user where user="zhangsan";);
複製表;作用 快速建表 備份表
格式:create table 庫.表 sql查詢;
create database dbbak; 快速創建庫
create table dbbak.uesr2 select from dc.uesr; 在dbbak這個庫裏克隆一個dc庫裏的表
create database dbbak.uesr3 select from dc.uesr where 1=2;
create database dbbak.uesr3 select name,uid from dc.uesr limit 3; ##備份dc.uesr表裏的前三行
庫名.表名 列表名,列表名 庫,表名 前三行
多表查詢:
select 字段名列表 from 表名列表; 迪卡爾集
select 字段名列表 from 表名列表 where 條件
create table studb.t1 select name,uid shell from user limit 3;
create table studb.t2 select name,uid,homedir from user limit 4;
show tables;
select from t1; select from t2;
select from t1,t2 where t1.uid = t2.uid and t1.name=t2.name;
select t1.,t2/homedir from t1,t2 where t1.uid
連接查詢:
左連接查詢 : select 字段名列表 from 表A left join 表B on 條件;
select * from t3 left join t4 on t3.UID=t4.UID;
右連接查詢 : select 字段名列表 from 表A right join 表B on 條件;