MySQL常用命令

mysql> SHOW ENGINES;        #查看存儲引擎命令
mysql> SHOW GLOBAL VARIABLES LIKE '%default%engine%';  #查看錶引擎
(1) 爲所有root用戶設定密碼；
                mysql> SET PASSWORD
                mysql> update mysql.user SET password=PASSWORD('your_pass') WHERE cluase;
                    FLUSH
                # mysqlamin
                mysqladmin -u root -p123456 password abcdef

(2) 刪除所有匿名用戶
mysql> DROP USER ''@'localhost';
上述兩步驟可運行命令：[shell]# mysql_secure_installation

                [shell]# mysqld --print-defaults    #如何獲取程序默認使用的配置
                ]# mysql -e "SHOW DATABASES;"   #命令行界面輸出命令結果；

SQL腳本運行：# mysql -uUSERNAME -hHOST -pPASSWORD < /path/from/somefile.sql
                    mysql> source /path/from/somefile.sql

獲取運行中的mysql進程使用各服務器參數及其值：
mysql> SHOW GLOBAL VARIABLES;
mysql> SHOW [SESSION] VARIABLES;
mysql> SHOW CHARACTER SET; #查看字符集
mysql> SHOW COLLATION; #查看排查規則

CREATE相關的常用命令：
                 CREATE DATABASE
                 CREATE EVENT
                 CREATE FUNCTION
                 CREATE FUNCTION UDF
                 CREATE INDEX
                 CREATE PROCEDURE
                 CREATE SERVER
                 CREATE TABLE
                 CREATE TABLESPACE
                 CREATE TRIGGER
                 CREATE USER
                 CREATE VIEW

相關查詢：

mysql> SHOW TABLE STATUS LIKE 't1'\G            #查看錶狀態信息：    
增加字段    mysql> ALTER TABLE student  ADD  age varchar(20) NOT NULL; 
mysql> CREATE INDEX name ON student (name); #索引的創建可以使用ALTER、CREATE命令創建
mysql> EXPLAIN SELECT * FROM students WHERE id=3; #確認是否有使用到索引進行查詢。
mysql> EXPLAIN SELECT * FROM student WHERE name LIKE '%X%';
mysql> EXPLAIN SELECT * FROM student  WHERE id=4\G

數據插入：

mysql> INSERT INTO student (name,sex,register_date) VALUES ('Jinjiao','M','2019-01-29');
mysql> INSERT INTO student SET name='Yinjiao',sex='F',register_date='2019-01-28';

更新數據：
` mysql> UPDATE student SET age=100 WHERE id=19;``

查詢：

mysql> SELECT NOW();    #顯示當前系統時間。
mysql> SELECT  DISTINCT sex FROM  student;   #去重查詢
mysql> SHOW GLOBAL VARIABLES LIKE 'query%';   #命中個數
mysql> SHOW GLOBAL STATUS LIKE 'Qcache%';     #緩存命中率查詢
mysql> SHOW GLOBAL STATUS LIKE 'Com_se%';

WHERE 子句：

mysql> SELECT name,age,id FROM student WHERE age >10;
mysql> SELECT name,age,id FROM student WHERE age+10 >10;

分組聚合：

mysql> SELECT * FROM student GROUP BY sex;
mysql> SELECT avg(age) FROM student GROUP BY sex;

HAVING: 對分組聚合運算後的結果指定過濾條件；

mysql> SELECT avg(age) as aage,sex FROM student GROUP BY sex HAVING aage>20;
                    #aage 定義的字段別名
mysql> SELECT count(id) AS NOS FROM student GROUP BY id;
mysql> SELECT count(id) AS NOS,id FROM student GROUP BY id;
mysql> SELECT count(id) AS NOS,id FROM student GROUP BY id HAVING NOS>2;

升序與降序語句：
升序：ASC
降序：DESC
mysql> SELECT count(id) AS NOS,id FROM student GROUP BY id HAVING NOS>2 ORDER BY NOS;
mysql> SELECT count(id) AS NOS,id FROM student GROUP BY id HAVING NOS>2 ORDER BY age DESC;

查看錶結構：
DESCRIBE tbl_name;
DESC命令用於獲取數據表結構